Memoire Online - Impact of the type of the cross sectional profile on urban zones road

A dissertation presented in partial fulfillment of the requirements for the award of a postgraduate diploma in technical education option publics works (DIPETII)

CERTIFICATION

I hereby certify that this thesis entitled «IMPACT OF THE CROSS SECTIONAL PROFILE ON URBAN ZONES ROAD» has been carried out by OBOUNOU ASSOUMOU MoiseEdgard with registration number 13T0753 in the Department of Civil Engineering and Forestry Techniques and of the option Publics Works of the Higher Technical Teacher Training College (H.T.T.T.C.) Bambili, University of Bamenda.

Signature:............................. Signature:.........................

DECLARATION

I hereby declare that I am the sole author of this thesis. I authorize the Higher Technical Teacher Training College (H.T.T.T.C.) Bambili to lend this thesis to other institutions or individuals for the purpose of scholarly research.

I understand the nature of plagiarism, and I am aware of the University's policy on this.

I certify that this dissertation reports original work by me during my University project.

DEDICATION

ACKNOWLEDGEMENTS

This work wasperformedat the University ofBamendaandparticularlyat the Higher Technical Teachers Training College (H.T.T.T.C) of Bambili. In a challenging environmentanda limited time,the outcomeof thisstudy wasmade ??possible by thecontribution of many peoplewho have supportedmethroughoutthis ordealby theirmoralcapital,financial, andscientificequipment.

Ø To Pr.YAMB Emmanuel Head of Civil Engineering and Forestry Technics department, for his constant availability and his endless encouragement, confidence in ourplace, patience, and interest and vigor brought to this work. He guided me and advice throughout the course and writing it. It is her expression of my profound gratitude.

Ø To Dr. KAMDJO Grégoire, my Supervisor, for having offered me help and advice for this dissertation.

Ø All those which from near or from far contribute to the realization of this work.

ABSTRACT

Basing itself on the concepts of hierarchisations of the roadway network system in urban environment, this work presents the impact, the consequences that a bad structuring of urban space by road transportation systems can convey.

This thesis thus presents the dimensioning of the roads, at least the cross sectional profile, in urban environment under an aspect often neglected especially in our country Cameroun.

In order to support this work on a strong foundation, an observation was made on the town of Yaoundé the capital of Cameroun; a city which knows multiple problems in its daily functioning. These observations were based on the figures on the linear of roadway system of the city, the hierarchisation of the various ways components of the roadway network system of the city, as well as analyzes of the functionality of the plan of the city, system of transport of the city and road safety.

In order to be beneficial, by bringing something new, we completed this work withsome proposals of standard cross sectional profile for the various categories of ways constituting the framework of an urban space.

RESUME

Se basant sur les notions de hiérarchisations du réseau viaire en milieu urbain, ce travail présente l'impact, les conséquences que peut apporter une mauvaise structuration de l'espace urbain par des voies de communications routières.

Cette thèse présente donc le dimensionnement des routes, du moins le profil en travers, en milieu urbain sous un aspect souvent négligés surtout dans notre pays le Cameroun.

Afin d'appuyer ce travail sur une base solide, une observation a été faite sur la ville de Yaoundé la capitale du Cameroun ; une ville qui connait de multiples problèmes dans son fonctionnement quotidien. Ces observations ont été basées sur les chiffres du linéaire de voirie de la ville, sur la hiérarchisation des différentes voies constituants le réseau viaire de la ville, ainsi que sur des analyses de la fonctionnalité du plan de la ville, du système des transports de la ville et de la sécurité routière.

Afin d'être bénéfiques, en apportant quelque chose de nouveau, nous terminons ce travail par des propositions de profil en travers types pour les différentes catégories de voies constituant l'armature viaire d'un espace urbain.

TABLES OF CONTENT

LIST OF FIGURES

LIST OF TABLES

ABBREVIATIONS

PDUY 2020: Plan Directeur d'Urbanisme de de la ville de Yaoundé horizon 2020

GENERALINTRODUCTION

BACKGROUND OF THE STUDY

The roadway system is the whole of the road transportation routes serving a given space. Thus, when one speaks about urban roadway system, we refer to the whole of the highway network of the aforesaid urban space.

The roadway system in urban environment is characterized by the multiplicity of the forms thatit can cover. According to the importance of its influence, its localization within the urban space, it knows an active range of situations from the smallest access road of the residential district to the expressway leading to the downtown area.

Since many years already, the principle of hierarchisation of the road transportation routes in urban environment aims at specifying the functions of the ways with respect to their places in the transport system. Thus, we distinguish from there ways of transit, local distributers and access roads. This mono technical functional approach must be supplemented by an approach relating to the interaction between the road and the environment crossed.

The diversity of the forms of roadway systems represents the process of appropriation of the roadway system by the various functions which it fills. Thus, because the street service road knows a weak traffic, its space can be largely occupied by the parking of the vehicles of the residents. Its installation will have to thus emphasize this aspect of its use while on the way of transit on which circulation is dominating; we will tend to reduce to their smaller expression installations such the pavements or the plantations in order to allot the maximum of possible space to circulation.

PROBLEM STATEMENT

The problem thus posed in this work is that of dimensioning, of the design of the cross sectional profile of a roadway in urban area and of its impact on the output, on the functioning of the section road to consider.

It is therefore question of proposing a dimensioning which depend on the frequency of use, on function of an urban road way and neighboring social activity; of knowing how to organize, to set out distribution of a roadway (numbers of ways, installations to be brought) in order to make it practical according to the zone of localization and the time period considered, especially when it is known that the urban environment in Cameroon is characterized by a remarkable disorder.

· The alignment is a sight in plan of the highway design (the center line of highway, various widths) in its environment support. It is composed of a succession of segment of right-hand side (general alignments) connected by curves which are either of the clothoïdes or of the circles or a combination of both (clothoïdes and circles)

· The longitudinal section is a cut carried out longitudinally along the axis of the road (defined by the alignment) and perpendicular to the original ground. It consists of a succession of slopes and slopes connected by circular or parabolic elements and is conceived after the final choice of the alignment

· The cross sectionof a road is represented by the layout of the roadway and the original ground on an orthogonal vertical plan with the center line of highway. In other words, it is a cut perpendicular to the center line of highway and original ground (on the longitudinalprofile). It gives as other information, the various dimensions of original ground, projects, the gauge (width of the road), etc.

Thus, talking of cross sectional profile for a road project mean to integrate these three defined terms because the study of the cross sectional profile of a road could not be isolated from the longitudinalprofilewhich itself is dependent on alignmentof this road.

But, the problem as posed up will treat mainly dimensioning of the gauge, of the width of the roadway. In fact, throughout our document, we will speak about cross sectional profile with regard to the distribution, the number of ways and dimensions which comprise the roadway itself and various installations which can be annexed there in order to improve its effectiveness.

JUSTIFICATION OF THE CHOICE OF THE TOPIC

Our study isinfluenced by a contextin which Cameroon fixed itself as objective to be an emergent country at horizon 2035. The reaching of this major goal will be done by the achievement of multiple secondary or specific objectives as presented in the DSCE, in particular those having link with the urban development such:

· The development of the urban infrastructures (construction of 150 km roadway system and construction of 17000 social housing),

Thus, the urban development being made mainly by creation, equipment and the maintenance of the road infrastructure, it is therefore in this spirit that the DSCE envisages a number of km of urban roadway systems built since 2010 which will pass to 63 km in 2015 to 150 km in 2020.This urban growth will inevitably be done by the means of an increase in urban population (estimates making state of a rate of urbanization of 57,3% in 2020 according to the DSCE), and thus, of important urban displacements.

However, in this policy of the improvement of the frame of life on the national territory in general and in the various urban centers in particular, how to boost or how to improve the output of our cities which are not very productive with the sight of the multiple problems to which they face such as difficulties of installation of effective and durable transport system, the problems of traffic jam, etc.? In order to bring a solution to these problems, we propose to focus throughout this work on the installation of the roadway system which ascertains to be the structure carrying the urban development. How to improve the characteristics of the roads in our cities in order to improve their productivity? Which is the impact of the profile across a road in urban environment?

Such are the various questions which found the justification of the choice of the present thesis.

PURPOSE OF THE TOPIC

Just like it was underlined in the heading of this thesis, we will attach throughout this work to seek if the profile across a roadway in urban environment has an impact on its output.

The aim had here is that of presentingthe importance of the hierarchisation of the roadway network system of a city and the impact of its presence or absence on the functioning of the town. Indeed space being one of the major factors or the most important limiting factor of urban environment growth's, it is question of building roads allowing to evacuate a more or less important flow of vehicles and this with an optimal width because if the road is narrow, the evacuated flow is reduced and it is the function, the utility of the road which is called into question; on another side, if the road is too broad, the economic and socialaspects are the problems because of the costs of construction, of the operations of expropriations, compensations and displacements of the bordering populations.

The present study finds all its importance in the fact that it makes it possible to show the narrowness relation existing between the category of a way in urban environment, its width and its output. All this having for finality a profit so much on the financial plan, sedentary and social when designing and/or the refitting urban roads by the various competent services. Thus, instead of increasing a road independently of his category or his localization, we could either make particular lay out or to organize it better, which would make it possible to make important financial profits or then if necessary to precede any enlarging or installation work by a study of traffic in order to estimate and to envisage the efficiency of the aforesaid work.

RESEARCH QUESTIONS

What is the impact of the type of a cross sectional profile of a road in a urban zones area?

This main research question intends to answer the following specific research questions:

· Does the categorization of a roadway system of an urban area have an importance?

· Does the cross sectional profile, the width of a road and the various installations that it has, change its functionality in the urban area?

FORMULATIONS OF HYPOTHESIS

It is reminded that throughout our study we will limit ourselves to road infrastructures in urban environment. Indeed the hypothesis on which the present report will be based is the following one: the type of the cross sectional profilesof a roadway on urban zone have an impact on the output of the aforesaid road.

· The cross sectional profile, the width of a road and the various installations that it has, can change its functionality in the urban area.

FORMULATION OF RESEARCH OBJECTIVES

The main objective of this study is to present the impact of the cross sectional profile, the width of a roadway on the efficiency of a road in urban environment

· To underline and to present the importance of the hierarchisation of the lanes in an urban environment, then we will list the various parameters entering the process of hierarchisation of a lane in urban environment.

· Present a standard cross sectional profile, a width of a road and various installations that can change its functionality in the urban area. By-there, we intend to define for example, a number of ways having each one a precise function and according to the case allocated with a particular traffic (private cars, exclusive right of way, two wheels, etc.); once this traffic, this use to determine, we will allow ourselves to propose a dimensioning, a standard structure to adopt.

HYPOTHESIS TESTING APPROACH

In order to verify our hypothesis we will follow the following testing approach:

v Verification of the impact of the cross sectional profile on the functionality of the town.

v Verification of the impact of the cross sectional profile on the transport system.

GENERAL AUDIT APPROACH

v Generalities on roadway system and hierarchisation of road in urban environment,

CHAPTER I:THEURBAN HIGHWAY NETWORK: DESIGN, FUNCTION AND ORGANIZATION.

«What is awaits from a research task is the originality. It is not a question of a quality in oneself, but of a step: the purpose of a report, a thesis, an article, are to bring something new, of original. The originality is all the direction of the review of literature. It is necessary to master what was already made as regards research to be able to position its own research so that it brings something moreover, so that it is original (at the border of the knowledge and the not-knowledge)»(Dumez, 2011, p. 17).

Throughout our research task, in which the purpose is to discover or establish the existence of the relation between two common aspects of the urban roadway system: the gauge of a way and its output, we leaf through several documents, articles and theses going in the direction of our research. Thus, in order to be a scientist during this study, we have judge adapted to start by defining the term urban roadway system.

1.1. The urban roadway system: what is it

The roadway system is historically definite like the whole of the transportation routes of a territory given i.e. the whole of the infrastructures necessary to support the circulation of the goods and people in the aforementioned locality. However, in urban environment, the roadway system is collective before being an infrastructure dedicated to the only circulation; it is a social space which structure urban space(d'ARCIER, 1992). On another side, the roadway system appears being a basic urban transport infrastructure and like such, it is defined as being a fixed public installation being used to provide essential services(NOUNDJEU, 14 au 15 février 2011). From these definitions, it comes out that to have for object of study the urban roadway system, it is to make a study which will have to take into account several forms and point of view as well technical as social. The urban roadway system thus proves to be the carrying structure, tallies of the development according to the old proverb which says: «where the road passes, the development follows.»

In urban environment, that always applies and even with an impact much stronger because one very often saw real estate goods and others to be object of important speculations after the built of a more comfortable access road was restored. Bruno FAIVRE d'ARCIER (1992) puts forward this aspect developing and devaluing by the road in urban environment in his thesis la voirieurbaine: de l'accumulation à la gestionpatrimoniale. The roadway system is, consequently this network, this infrastructure of communication around of which will organize the life in urban environment (in all or if not, large majority of the circumstances). The urban roadway system will thus be characterized by its multifonctionnality, the multiplicity and the diversity of the users whom it gathers;In its thesis, B. FAIVRE d'ARCIER (1992) made a short summary of the various possible approaches of definition of the urban roadway system: like public domain, like infrastructure, network and space.

· In the approach of the roadway system like network, the roadway system is comparable with a whole of sections and crossroads primarily being used with circulation of the goods and the people to the means of modeof transport motorized or not.

· The approach infrastructure, which is prevalent for the town planning engineering, is based on the concept of network, but privileges the roadway system like basic infrastructure rather, support of other network (electricity, water, telephone, etc.)

· In the approach of the roadway system like space, prevalent for the architects and the town planners, the roadway system is seen like a volume and constitutes an element of the urban landscape. In addition to that, for the town planners, the urban development and of its activity is closely related to the conditions of accessibility in a context where it is necessary to differentiate the places of residence and the places from activities.

· The approach in terms of domain which is used as pillar to legitimate the intervention of the public authorities because it allows given again the public space which is the roadway system, its place vis-a-vis approaches of the functionalist types.

The following quotation, from the general guide of the urban roadway system as cited by(d'ARCIER, 1992, p. 2)thus appears to be, we think it enough adequate to summarize the point of view supported up: «what characterizes a street, it is its complexity the multiplicity of its roles. It accommodates activities which should be served, it is to border of trade, it shelters the walk or the rest of the townsmen, it ensures the service road of a district while supporting calm residents, or even it runs out an important traffic that it is necessary to reconcile with a correct environment with the inhabitants».(CETUR, AIVF, 1988)

Of all what precedes, it is thus clear that the concept of design of street could not be universal or at least, should more or less adapt according to whether one is in such or such medium where the social behaviors and the daily intrigues differ, question of guaranteeing the safety of the motorists and the residents which interact both with the road: it is clear that we does not drive in the same way on an urban boulevard as on one street crossing a market or a road access in full district. The design will have to implementfactors which will have to make recognize with the motorist function (service road, fast track, etc.) of the way where it is, and thus, to lead it to adapt its speed which would be finally only the translation, in terms of control, of this function.With respect to the road safety, it is important that installation makes it possible to the motorists to correctly identify nature and the uses of the way which they borrow so that they can anticipate, to some extent, the inherent risks has this space and thus to adapt their behavior (in particular their speed) has these characteristics (the space). In their articles,(BRUSQUE, MENARD, MONTEL, DUBOIS, & RESCHE-RIGON, 1997)starting from an experimentation of categorization carried out using catches of sights of urban sites, identified the categories of ways which the various users and the criteria from differentiated which these categories are constituted. They pushed their work further by evaluating also up to what point night environment modifies the mental representations than the users have this space.

1.2. Parameters to be considered during the dimensioning of the width and the appendices of a road in urban environment

Because the roadway system in urban environment is in the center of multiple waiting, it is being a subject transversal, object of several centers of interest and fields of studies.

· In space economy and economics of the transport, the roadway system is largely taken into account like network of circulation. In these two sciences, the creation and/or the improvement of the quality of a transportation route (road way) have for principal drank the production of easement rights to space and the reduction of the constraints of distances. The roadway system, its quality and its quantity are thus to have a contribution, an economic impact on the exchanges, the localization of the activities and the valorization of spaces.

· The town planners as for them, foresees the creation of transportation route like factor of urban development. Indeed, they have there recourse like tool of planning and structuring of urban space.

· Civil engineering as for him perceives installation the roadway system like a transport infrastructure and like such, the aim had during the construction of a road remains the improvement the speed of course and comfort as well in urban environment, sub urban as in open country. Like result, we have «a very road treatment, which denies practically the existence of other uses, or segments the roadway space in two components which is unaware of, the roadway and the remainder»(d'ARCIER, 1992, p. 5)

In order of not to be dispersed in our study, we will take into accounts (generally) two of the four approaches of definition of the roadway system stated upper: approach of the roadway system like space and that of the roadway system like network:

Indeed, insofar as the roadway system appears being to regard as a space, the aim had during its creation is to conceive a roadway system which will fit (with esthetics) in the urban panorama just as it will have to make it possible to serve different the poles from activities composing urban fabric: zone of activities, residential zones, retail parks, etc.

On another side, to foresee the roadway system from the infrastructure point of view supposes that a good road, a well done roadway system should allow the circulation of the goods and people within better times (speed factor) and under conditions of optimal comfort and safety.

This double aspect can be retaking and further in a rather realistic way in two models(STRANSKY, 1995) :

A first model which has a representation, «where the street is cut out in fragments and absorbed by the pieces which border it, the «circulation» dimension of the urban space-roadway system can only miss.» (STRANSKY, 1995, p. 14)and a second says model of traffic where, all that is not flows car and strict roadway with the direction of the term (expressed of «number of ways») is evacuated.

Which are the stakes, the impacts of installation, the improvement of a «cross sectional profile»^1(*)of a road in urban environment?

This interrogation rests on the difficulty of a bond between two characteristics of the roadway system in urban environment:

On a side, we have his function which is to seek the displacement of the goods and the people from one place to another of the city by the means of vehicles motorized or not.

Here, it does not matter the sector, the frame of life crossed, the priority remains granted to the traffic which must circulate under optimal conditions and deadlines reduced.

On another side, we have his form which it, deal with its configuration, dimensions which are to allot to him, «its cross sectional profile». The governing idea here remains that of the priority of the place where the road passes: When it is a medium where it does not interfere with the framework of life of the bordering populations, then there is no objection so that it is as broad as possible^2(*)(with all that implies like speed of circulations and noise pollutions).Only when it has to crossmiddle assiduously attended by the Man, it must adapt.

Only, formulated in this manner, this question proves to be rather broad and dispersed to be able to be used as starting point with a research task. In order to limitit extent, we (in the sight of the type of research task^3(*) of this memory) will subdivide this principal interrogation into questions, the objective being to best encircle it.The options selected are in particular: is it necessary to treat influence of the form on the function, or that of the function on the form?

The difference between these two alternatives lying in the fact that, in the first case, the idea is that of a space configuration of the roadway infrastructure taken as being a fixed data which one wonders whether, which and how are the influences which it has on the characteristics of the traffic which it supports; a priori, and whatever the definition of the traffic, this type of study concerns the behaviors of the motorists placed in a given situation. In the second option, research is evolutionary since it would be a question of studying the process of evolution of the space configuration (in terms of installations, inter alia) of rue when it changes function-displacement. We chose to interest us, in this memory, with the second aspect of the question; that of a possible influence of the function on the form.

The encyclopedia(LAROUSSE, 2009)definite the city like a relatively important agglomeration and whose inhabitants have community activities diversified in particular in the tertiary sector.

This concentration of inhabitants in a rather reduced surface creates important constraints more especially as it is necessary to manage and ensure displacements of the aforesaid populations from one point to another of the agglomeration and for various reasons. One of the means if not the principal means of organizing and of making profitable an urban space remains by creating there transportation routes which will have to fill of the different functions.

1.3. Functions of a roadway system in urban environment

Indeed, during the estimates in study of traffic with the macroscopic model^4(*)(COSTESEQUE Guillaume, Avril 2012), the streets (minors) are supposed to be non-existent and neglected because not being useful which the vehicle has to fold back on the main roads (object of the study of traffic). It is to say that during a displacement from one point A to a point B (relatively distant) of a city, a motorist starts at the time of the first minutes of his travel by folding back himself on one of the «main roads» in order to go faster and carries out there most of his travel. Arrived at the end of the course, it is folded back towards the small streets which will thus enable him to arrive at destination. One can consequently speak: «of bursting and folding back»(STRANSKY, 1995).

Thus described, urban space is connected with a whole of block made up of the various urban sectors such the downtown area, the residential zones, etc. which the lanes will have to connect between them.

It is thus clear that the roadway system in urban environment will have to fulfill various functions namely:

· A circulatory function because the streets are judicious to support the displacements carried out by the motorized vehicles or by the alternative modes (bicycle, walk, transport, etc.). This function often induces stereotyped installations being based on the separation of the modes: a roadway for the motorized users, of the bands or cycle tracks and the pavements for the pedestrians.

· A function local life where the streets are also to regard as public spaces, places of animation, user-friendliness and meetings, relaxation, walk and even sometimes of plays for the children. This local life pains to exist vis-a-vis installations of the «road» type which privilege the car.

Practiced and/or authorized speeds are adapted often little to the cohabitation between functions circulatory and local life.

However the development with the profit of this function of local life answers 3 stakes (Direction départementale des Territoires de l'Ain, 2013):

· A stake of social cohesion: The experiment shows that the more speeds are raised, the more the axes of circulation are felt as urban cuts which do not support the social relations of vicinity. The moderation speeds thus makes it possible to weave more easily of the bonds (space, social) to facilitate the meeting with others.

· A public health issue: Excessive speeds induce a deterioration of the quality of the frame of life by accentuating noise pollutions with consequences often underestimated on the human health. Sound environment in night period has an influence on the quality of the sleep. The moderation speeds in medium of social life thus proves to be of a public health issue.

· A stake of public safety: The moderation speeds supports the reduction of the number and the gravity of the traffic accidents. It contributes in particular :

From these various functions, it will thus result from this the different characteristics from the roadway according to whether one is in a zone with strong pedestrian frequentation or machines with two wheels as in zones residential or on the other hand that one is in zones has strong traffic where the use of the car remains dominating such on the loop lines, ways of penetration and those leading towards the urban center where the practice of an high speed remains necessary and/or authorized.

From this concept of difference in characteristics of the roadway according to the traversedmiddle, we can say that it results from this the notion of hierarchisation of the roadway system which is particular with urban environment. Indeed, the road which hardly starts to adapt on arrival of the car will have to be constrained now in turn to adapt to the frequentation pedestrian as Bruno d'ARCIER underlines it(d'ARCIER, 1992)when it quotes A. GUILLERME at the time of a communication to the seminar of the Urban plan «City and transport» of March 18th, 1992 which, speaking about the first version of the highway code, stresses that the pedestrian had the right to be informed on arrival of a car by an aural signal and that him in return, has the duty to leave him (the car of course) the passage. To improve the circulation terms inside the agglomeration it is advisable to support the installation of the roadway systems on their hierarchisations; Hierarchisation which is conceived according to two criteria namely:

· The function of the way according to the type of supported traffic (transit, exchange, internal service road) and the characteristics of its installations.

1.4. Various categories of ways in urban environment

The junction between the two criteria enumerated upper will thus make it possible to distinguish four categories of ways:

· Access roads to the agglomeration built for the through traffics such the interpolate connections which have origins and/or external destinations with the agglomeration and which are consequently, the privileged field of the car.

These axes, for their integration and the prospects which they offer, can cover two categories:

· Loop lines which protect the heart of the agglomeration and the other secondary centers: they have as a function to protect the urban centres from parasitetraffic and to connect between them axes of penetration. These ways offers a time-saver for the exchange and through traffic while releasing the centers of the agglomeration of any additional and useless traffic. Their installation is completely integrated into urban infrastructure; speed is restricted there with a limit lower than the access roads to the agglomeration. On these ways, the principal characteristic is the optimal research of the fluidity of circulation.

The installation of the crossroads between the loop lines and the penetrating ones are paramount. To encourage with the use of skirtings, it would also be necessary to offer a good legibility to the crossroads and to set up an effective marking out.

· Ways of penetration towards the centers which will have to support constraints arranged hierarchically according to the density of the crossed middle: The local life on these ways becomes more perceptible. «Generators» of displacements (trade, services and public equipment) fit bit by bit in the urban infrastructure. The soft modes can be present, but the place of the motorized vehicles prevails. Dimensions will have to thus be generous for the motorized vehicles, but the characteristics of these ways (bordering accesses very few, restriction of side parking...) would not make economic a speed limit to 30 km/h. One can classify in this category certain avenues and important ways inter districts as well as the majority of the ways of zones of activities.

· Access roads intern with the various communes or constituent districts the agglomeration. With this scale, the roadway system is regarded as being a public space where a balance between the circulatory functions and local life must prevail (cohabitation between the various users). The description of the stakes showed that a limitation to 30 km/h constitutes a good compromise between the motorized traffic flow, the safety of the pedestrians, cyclists and the quality of the frame of life in the districts. This typology of installation can apply to a very broad range of ways: service roads of residential district, ways of retail parksand streets of downtown area where bordering activities (trade, services, tourism...) a frequentation important pedestrian and cyclist induce. She can also have the aim of dissuading the through traffics when those have more adapted alternative routes.

Source: MANDELBROT, B. The fractal Geometry of Nature, W.H. Freeman, New York, 1983

1.5. Hierarchisation ofroadways in urban environment

The conclusion at which we arrives according to a study of STRANSKY (1995), is that the behavior of a motorist, which can result in speed that it practices on an axis given, is influenced by the elements of the surrounding visual scene and thus can force it to adopt changes. From this assertion, it results from it that speed practiced on a way is function of the installation of this way. Thus, it appears for reasons of functionalities, safety and economy, useful to adapt each section of roads during its construction or of its requalification to the function awaited from this one (influence of the function on the form): from where concept of hierarchisation of the ways in urban environment.

Indeed, it is at the time of Chatre of Athens in 1933(CORBUSIER, 1957)which one really starts to grant an importance to the adaptation of the road to the car. And due, this one did not correspond any more to the old characteristics of the street as well by its new geometrical characteristics, mechanics as by its speed.

The «rule of the 7V» is one of the first rules of hierarchisation which was formalized by UNESCO in 1948(d'ARCIER, 1992, p. 27). It consists of:

V.2: municipal, standard creation of arteries essential for an agglomeration

V.3: held primarily for mechanical circulations, they do not have a pavement; no door of houses or buildings opens on them. Regulating fires of colors are laid out the every four hundred meters, thus allowing the vehicles a considerable speed. V.3 has as a consequence, a modern creation of town planning: the sector.

V.5: penetrating in the sector, it drives the vehicles and the pedestrians to the doors of the houses, with the assistance of V.6

V.7: feeding all with length the green zone sees where are the schools and the sports.

By what precedes, it appears that the hierarchisation of the roadway system in urban environment does not date nowadays and wants to be to be a means of representing a network of ways starting from several beforehand definite criteria. It is a tool for analysis, meeting a need for classification and organization of the network of circulation. It can also be useful during the programming of installations, to which it is used as reference(CERTU, 2008). It thus makes it possible to obtain profits in terms of safety, in particular by a greater coherence between classes of ways and thus by a better legibility of the network for the users. Nowadays, the possible forms of hierarchisation many according to whether one is in urban environment or are perished urban.

For the ways in urban environment, the forms of hierarchisation are more complex. Thuswe have a hierarchisationwhichcanbe:

· Functional according to the type of connection, for example: primary ways (structuring), secondary (distribution), tertiary sector (service road);

· By typology according to the influence of the way in a logic of urban development (urban fast tracks, boulevards, avenues, streets...) ;

· By typology of way according to the nature of the bordering frame (in withdrawal, alignment, height...);

· By typology according to the social practices (local life, places emblematic...) ;

· By an analysis multicriterion integrating the multiple uses and needs for public space.

Hierarchisation rests more and more on the taking into account of two principal functions: the function «circulation» which milked with the flow that can run out the way, and the function «local life» which is concerned with impacts that the road has on the traversed environment. It is thus question here of safety of the residents.

One defines the class of way according to the preponderance granted to such or such function. The characteristics desired for these classes must correspond to the objectives initially envisaged in the documents of city planning namely: share roadway system, development of the alternative means of transport, safety of the users.

Today with the example of the European countries, Germany in particular, a hierarchy resting on two great levels is usually advised with:

· main roads where the circulatory function is dominating on the function local life. The organization of space on these ways is structured in theory (crossroads, crossed pedestrians...);

· zones with alleviated circulation, generalized on most of the urban territory, but also of the zones of meeting and surfaces pedestrians, to privilege the local life and to ensure the safety of the various uses of the network, by moderating speeds and by eliminating the parasitic traffics in these zones.

CHAPTER II: METHODOLOGICAL CONSIDERATION

2.1. Description of the course of the data-gathering

By who will be carried out measurements? Who holds the various databases necessary to the study? Which steps is it necessary to get them? ...

Such were the questions which should prevail during the proceed of the data-gathering.

The people to«investigate» should be selected on the basis of data and preliminary library search, i.e. according to their susceptibilities to have resort to the use of the data specific to urban environment or other various data for which we had needs for our study. Among the preselected organizations, we had: the MINDUH, different CameroonianCity Council in particular that from Yaoundé, Douala Bafoussam and Bamenda; various communes of district and different research department and companies having taken part in construction and/or realization of various works requiring such data in particular EGIS, MAETUR, etc.

At the end of this pre investigation, it was reported to us that the Yaoundé City Council had various document of city planning among which figure the «Plan de Déplacement de la Ville de Yaoundé»: a document which the development required the realization of the almost totality of the investigations and data we needed for our study. This document, plus the «Plan Directeurd'Urbanisme de la ville de Yaoundé 2020» and the «Plan Somaired'UrbanismedeYaoundéNord» et «Plan Somaired'Urbanisme de Yaoundé Sud» which we already had should thus constitute a reliable source data enough for the realization of our study

So, rather than to remake the investigations and research (which would cause important waste of time and money) we decided rather to resort in the search of this document (the «Plan de Déplacement de la Ville de Yaoundé»).

However, because of quality of the investigations carried out, of the quantity of data provided and finally of the relativerecent of the studies (compared to the other available), we chose to work, throughout this memory, much more on the basis of the studies made at the time of the realization of the PDU.

2.2. Description of the environment targets of study

The selection of the environment of study will have been strongly influenced by the availability of the data necessary to unfolding of the study.Once all these data defined, and their availability checked, the following stage was to make the choice of a ground of study which would gather the various criteria to be defined for the model. Moreover this field of study should allow the application of the various methods of investigations and data acquisition.

Thus, at the end of the preliminary stage of pre-collection of the data, with the sight of the importance of the database put at our availability we decided to make the town of Yaoundé, our environment of study.

Capital of Cameroon and second bigger city of the country after Douala, Yaoundé shelters the essence of the administrative superstructure of the country and part of the head offices of the enterprises. It is also the chief town of the Centre region. Its economic activity, the daily mobility of the inhabitants and the offer of transport are strongly influenced by the presence of the central public administrations.

The administrative territory of the Yaoundé City Councilcovers a surface of 28.798 hectares. The city is located in anirregular relief, plates staged between 700 and 800 m of altitude and the mountainous solid masses reaching up to 1200 m of altitude. If the site presents a certain charm, it imposes constraints on infrastructures and transport. It increases the cost of the transport infrastructures which must be lengthened to avoid too stiff slopes and also to include several works of crossing. Lastly, the irregular relief increases the painfulness of the walking and the use of the bicycle. In 2002, the urbanized site occupied nearly 16.000 hectares, that is to say 56% of the administrative surface of the city. The average density of urban infrastructure was of approximately 100 inhabitants per hectare. This weak density leads to a lengthening of the distances from displacements for the population. The climate of Yaoundé is subtropical moderate with two dry seasons in alternation with two wet seasons and of precipitations exceeding 1.600 mm on the whole per year. The strongest rains intervene in September and in October, period of beginning of school year. The temperatures oscillate between 18°C and 28°C during the wet seasons, and between 16°C and 31°C, during the dry seasons.

In 2005, according to the results of the 3rd General Census of Populations (RGPH), the population of Yaoundé was of 1,8 million inhabitants, that is to say approximately 10% of the population of Cameroun. Between 1987 and 2005, that is to say 18 years, the population of the city has almost triplet, recording an intercensal growth annual average of 5,9% per year.

2.3. Description of the instruments of research

In order to carry out the collection of relative data to the creation of a suitable and adapted model of study, it will have been necessary the use^5(*)of various and different instruments according to whether needs data relative to a precise field.

Thus with regard to thetechniques of collection of variables of traffic, theprincipal source of data of traffic is the collection by equipment indicated under the generic term of sensors. In general, they are elements sensitive to a physical quantity: speed, the presence, or passaged' a vehicle. We distinguish:

2.3.1. Pneumaticsensors

Figure 2: A pneumatic sensor for automatic countingSource: Cours de route 2006 Université d'Orleans I.U.T de Bourges

This type of sensor consists of a rubber cable tended across the roadway and connected to a detector; the crushing of the cable causes an overpressure detected by a pressure gauge actuating a relai: this system thus counts the number of axles which pass (we divides by 2 to obtain the number of vehicles). Easy to pose and autonomous, this system is rather expensive and fragile because it can betorn off by a heavy vehicle, moreover, the error ratecan go beyond the 20% in saturated rate; what seems to us rather enormous: because a variation of a few percentages is sufficient to distinguish a fluid rate from a saturated rate.

2.3.2. Electromagneticloops

It consists of an inductive loop drowned in the carriageway surfacing, detecting the variation of the electromagnetic field caused by passaged' a vehicle (metal mass), which results in a «crenel of tension» whose characteristics make it possible to know the length and the time of passage of the vehicle. The installation of two inductive loops close one to the other makes it possible to know the instantaneous speed of the vehicles. The technique of the electromagnetic loops has the advantage of being cheap and robust (important lifespan); its great weakness is the dependence of its reliability to quality of the adjustments and maintenance.

2.3.3. Acoustic detectors

Of current employment in Japan but not very widespread in Europe and in the United States in spite of the facility of their maintenance, these detectors are consisted a directing antenna emitting an ultrasonic wave; part of this wave is considered at the time of passage of a vehicle in the surface of detection of the device; a fraction of this considered wave is collected by a receiver, which makes it possible to calculate the occupancy rate of the road.

2.3.4. Radars with Doppler-Fizeau effect

It is about a directing antenna emitting an electromagnetic wave whose a fraction - after reflection on the vehicle - is consequently collected by the same antenna; the difference between emitted frequency and considered frequency is proportional to the instantaneous speed of the vehicle, which makes it possible to calculate the value of the speed of the vehicle with a precision of about2 km/hfor speeds lower than100 km/h.

Concurrently to these techniques of automatic countings, there exist also techniques of countings said «at sight»; we gather under this heading all the techniques based on the vision, natural or artificial, which includes the direct observation in situ, by air photography or via fixed cameras installed at certain places of the infrastructure.

In what concern the linear of the roadway system and similar data such the populations of various zones, etc. we will use software of numerical cartography and Geographical Information System in particular ArcGIS™ or Mapinfo™ (which is used by the YCC) in order to obtain data relating to it.

Obtaining data on operation of the transport system and the road safety in urban environment, was made possible by the means of the realization of investigation of ground near households and sectorial of the field of the urban transport in particular the taxi drivers, of motor bikes, etc. brief of the various actors and users of the various modes of displacements intervening in the field of the urban transport.

Within the framework of our work, it is to be recalled that we much more had recourse to final the diagnosis report of the Plan of Urban Displacement of the town of Yaoundé which comprised already the results of the various investigations carried out at the time of the study.

2.4. Description of the model of study

If it is true that the «cross sectional profile», the installation of a road can have an impact on the output of this road in urban environment, this impact should be able to be checked or to be highlighted by the construction of a model which should make it possible to confront this road with its output according to its category and of the hours when the frequentation is maximum there.

The model adopted for the checking of the basic assumption of the present report will thus have to take into account:

2.4.1. The legibility and functionality of the plan of the city

The first of these requirements should allow an evaluation of thefunctionality and legibility of the plan of the city and this through data on the quantity and quality of the roadway network of the town of Yaoundé.

Consequently, this criterion emphasizes the importance of the structuring of space by suitable transportation routes which thus make it possible to make readable the plan of the city just as it allow a better functionality.

2.4.2. Requirements of temporal delimitation: rush hours.

This criterion is relating to the period of collection of the data: the data obtained should make it possible to know the capacities of traffic at the hours of maximum frequentation.

· To move away from the edges (January, December) and to move away from the tops (July-August)

· The months representative of the year are the months of: February, April, October,

· The days representative of the week are: Thursday - Friday - Saturday or Sunday - Monday - Tuesday

· The hours representative of the day are 7:00 - 10h or 16:00 - 19h what corresponds to the rush hours.

2.4.3. The functioning of the transport system

This criterion is relating to urban mobility in the city because it should enable us to evaluate mobility in the city object of the study.

The models of simulation of traffic are important tools of which the use is not limited simply to the planning of the transport infrastructures. Daily, they can also be used for the regulation of the traffic by testing the effects of technological innovations such as the Intelligent Transport systems. They can finally be more generally used for the city planning in general and the localization of the services and the urban activities.

Thus, are studied there major elements for the urban mobility such the offer of transport, the demand for transport, the traffic motivations, the existing means of transport and reasons justifying their choice during a displacement and finally the various zones between which accomplishes transport in the zone of study. The delimitation of the zones of transport constituting the key factor of this criterion, we renewed the model made up at the time of the investigations carried out at the time the production of the Urban Plan of Displacement of the town of Yaoundé.

This model of displacements in Yaoundé aimed at the simulation of the traffic on the roads and the railroad in the city in order to test scenarios of installation of the offer of infrastructures to check that they would answer well the present needs (2010, date of realization of the document) and futures of urban mobility. For this simulation, the Consultant had actually built two models.

· The first is a static model, (traditional tool of modeling based on a step at several stages which makes it possible to estimate the various types of traffics on the whole of the network of roadway system and of the rail network) which simulates the transport demand during the rush hour on the whole of the network of the city and makes it possible to estimate the various types of traffics on the whole of the network of roadway system (mainly); It thus proves to be an extremely powerful tool to appreciate the impact of specific installations on the general flow of the traffic.

· The second is a dynamic model of micro-simulation the purpose of which is to optimize the time of crossing of the crossroads and the geometry of the intersections which are often at the base of congestions. This optimization, which is made by a simulation of traffic on precise sections is obtained graces to the results (in flow of vehicles) of the static model.

The two models were gauged over the year under review (2010) and were then used to simulate the situations by 2030.

Thus, the zone of study defined during the courses of this investigation was consisted of the distribution in districts defined by the GIS of the YCC. This distribution includes 87 internal zones and 9 external zones (related to the penetrating roads). In order to better represent the traffic in the downtown area, the Consultant moreover divided the zone of the administrative and commercial center into three zones.

The table hereafter gives the names of the zones finally retained for the study, while the chart it shows the extent of the zone.

AHALA	MBALLA 1	NGOUSSO 1	RN1 Nord
AWAE 1	MBALLA 2	NGOUSSO 2	RD46 NE
AWAE 2	MBALLA 3	NKOLBISSON	RN10 Est
BASTOS	MBALLA 4	NKOL-EBOGO	RD11 SE
BITENG	MBALLA 5	NKOL-MESSENG	RN2 Sud
BIYEM-ASSI	MBANKOLO	NKOL-NDONGO 1	RN3 SS
BRIQUETERIE	MELEN	NKOL-NDONGO 2	Route Kribi
CITE-VERTE	MENDONG 1	NKOM-KANA	Route Douala
EFOULAN	MENDONG 2	NLONGKAK 1	6751
EKOUDOU	MESSA CARRIERE 1	NLONGKAK 2
EKOUMDOUM	MESSA CARRIERE 2	NLONGKAK 3
EKOUNOU 1	MESSAME-NDONGO	NLONGKAK 4
EKOUNOU 2	MFANDENA 1	NSAM
ELIG-EDZOA	MFANDENA 2	NSIMEYONG 1
ELIG-ESSONO	MIMBOMAN 3	NSIMEYONG 2
EMANA	MIMBOMAN 1	OBILI
ESSOS	NKOMO	OBOBOGO 1
ETAM-BAFIA	MOKOLO	ODZA
ETETAK 1	MVAN	OLINGA
ETETAK 2	MVOG EBANDA	OYOM-ABANG
ETOA-MEKI 1	MVOG-ADA	SIMBOCK
ETOA-MEKI 2	MVOG-BETSI 1	TSINGA 1
ETOUDI	MVOG-BETSI 2	TSINGA 2
ETOUG-EBE	MVOG-MBI	CENTRE ADMINISTRATIF 1
GRAND MESSA	MVOLYE	CENTRE ADMINISTRATIF 2
KODENGUI 1	NDAMVOUT 1	CENTRE ADMINISTTRATIF 3
KODENGUI 2	NDAMVOUT 2	CENTRE COMMERCIAL 1
KODENGUI 3	NGOA-EKELLE 1	CENTRE COMMERCIAL 2
MADAGASCAR	NGOA-EKELLE 2	CENTRE COMMERCIAL 3

Source: Communauté Urbaine de Yaoundé: Yaoundé 2020, Plan Directeur d'Urbanisme, AUGEAINTERNATIONAL-IRIS CONSEIL-ARCAUPLAN, 2008

2.4.4. The road safety

The system of circulation is made of constant confrontation between the various elements constituting it namely: drivers, pedestrians, environment of circulation, the infrastructures support of circulation and vehicles. The road safety will have to aim reducing to the minimum, the number and the consequences of the dysfunctions of the system of circulation (usually called road accidents) between these various inputs of the system of circulation.

Modeling in this case will thus consist of a simulation of a confrontation being able to lead to a traffic accident. Thus we will try to have the potentials causes of them in particular those having milked to the infrastructures and the environment of circulation.

CHAPTER III: PRESENTATION OF THE RESULTS AND DISCUSSION.

At the sight of all that was presented up in particular the importance of a hierarchisation of the lanes in urban environment and the different categories which constitutes or should constitute an urban space, we think that the structuring, the installation and the adequate hierarchisation of the roadway system of a city have an impact on his functioning. Indeed, this impact or rather these impacts is found on several scale and aspects among which on the functioning of the aforesaid city, the field of road safety etc.

3.1. The legibility and functionality of the plan of the city

The YCC has a GIS exploited under the software Mapinfo™. It is indicated on the roadway system, public equipment, the marketing activities, the school and medical infrastructures...

This GIS is thus a reliable source of information on the roadway network of the town of Yaoundé. Indeed, according to its data, the roadway network of the town of Yaoundé is estimated at 2.536 km of lanes of which 755 km are paved. Even if, part of linear of the total roadway network of the GIS is out of the territory of the YCC, the network of the city is being quite higher than the advanced figures in all the municipal official documents, in particular 435 km of paved routes and 465 km of unpaved routes.

Therefore, if we consider the whole of the roadway network of the city, the level of coverture proposed in Yaoundé is in the average of the developing countries. However, the covered network of the city has a lower level of cover among to the world.

The roadway network of the town of Yaoundé is arranged hierarchically according to several types of ways. Although there do not exist formal basic for this classification within the YCC. Wedistinguish there:

· the National roads, which are urban portions of the national roads, long of 65 km, including 61 km paved;

· A secondary roadway system, having an overall length of 78 km, of which 57 km are paved;

Table3:Hierarchisation of the highway network system of the GIS of the town of Yaoundé

A weakness in the organization and the structuring of the roadway network system makes it possible to highlight important dysfunctions such:

· Problems «of use of the ways» i.e. important loads of traffic on unsuited axes;

· Problems of legibility and marking out: because in a badly structured space, it becomes difficult to know «spontaneously» if we are or not on an main road, standardized crossroads and the great number of roundabouts disturbing the comprehension of the routes network;

· Difficulties to make cohabit on the same space cars and other alternative modes of displacements.

It thus appears essential to be concerned with hierarchisation of the roadway network system to put in adequacy the treatment of a way and the functions which it ensures in the network.

· Ways with large transit which have as roles to direct the national and regional transit through the city (flow which have nothing to doin the urban perimeter but are just pass through ) just as it will have to give access to the urban perimeter since and towards outside. The objectives of the construction of this type of work are the fluidity and the safety of the light vehicles and the heavy trucks, of the exchanges satisfactory with the perimeter around. Thistype of ways has the characteristic of a highway

· Penetrating ways which have as roles in the roadway network system, to allow an exchange between the transit ways and the internal road network of the city. These ways have characteristics of fast tracks.

This hierarchisation brought back to the context of the town of Yaoundé is almost the same. Thus, we distinguish four classes there; from whose only the two first ways are regarded as being structuring ways of the agglomeration. We have there:

· The primary Roadway system: it includes the whole of the ways which constitute the principal grid of the urban highway network: national roads, the principal penetrating, by-pass, ways connecting between them principal public equipment and with the great centres of population;

· The secondary Roadway system: the secondary network of roadway system here ensures the connection between the zones bordering located inside the meshs on the primary distributers. Connected to the primary network of roadway system, it supplements the structuring grid of the city;

· The tertiary Roadway system: the tertiary network is a network of service road which makes it possible to reach in the middle of the various districts of the city;

· Particular Roadway systems: the ways of the industrial parks, of the zones where circulation is partially or completely prohibited, are the subject of a classification and a specific standardization.

The current network structuring town of Yaoundé is equipped with 270 kilometers structuring ways; is 13% of the total linear of the roadway system of the city including 120 kilometers of primary ways and 150 kilometers of secondary roads. The current configuration of the network shows a concentration of structuring ways in the center town area. Indeed, the administrative center and the shopping mall are best equipped in broad avenues and paved boulevards. Because of their localization, on one hand, and limited number of loop lines, on the other hand, they constitute the zone of passage of important flows of traffic.

The structuring network of the town of Yaoundé appears being thus relatively weak. Moreover, in this classification, 10% of the total network are consisted of the primary distributers (and national roads), against 3% for the secondary roadway system what is rather inadequate because the primary distributers having to be lower than the secondary roadway system.

As corollaries of this insufficiency of the structuring network of the city, we have a saturation of the principal access roads to the city just as it is noticed there a presence of traffics and misfit practice sources of multiple traffic accident and a functionality of the plan of the city which appears rather poor.

Indeed, a study of the various types of traffic having an origin and/or an internal or external destination of the city reveals that the inbound traffic towards outside amounts to approximately 4% of the total traffic. Moreover, 0,4% of the counted total traffic are a through traffic thus inappropriate because being a traffic having an origin and an external destination at the city. This figure, in spite of that, has to being raised to take account of the night traffic, since the trucks of more than 20 tons, like the timber trucks, cannot circulate in Yaoundé during the day. This through traffic can be estimated at approximately 1% of the total traffic by the night counting carried out during the investigations. The buses and the minibuses have a ratio of exchange close to 35%. Transport by bus ensures the service road close to Yaoundé and that of the big cities of the country.

	Intern	Importation	Export	Transit
Motor bikes	94,9%	2,5%	2,5%	0,0%
Cars and 4X4	92,9%	3,4%	3,4%	0,3%
Taxis	95,3%	2,2%	2,2%	0,3%
Mini bus	65,8%	16,4%	16,4%	1,4%
Bus	62,8%	17,9%	17,9%	1,4%
Van	88,8%	5,5%	5,5%	0,2%
Trucks (=2 axles)	78,4%	9,8%	9,8%	2,0%
Trucks ( 2 axles)	77,8%	11,1%	11,1%	0,0%
Trailers	100%	0,0%	0,0%	0,0%

Moreover, the GIS of the YUC provide information on the state of 267 kilometersof ways. Thus, even if more than 90% of this linear is judged in a good or average state, it should be recalled that the analysis related only to 11% of the total highway network and 72% of the structuring network.

Table5: State of the road in the town of Yaoundé according to the GIS of the YCC

Class of ways	Good	Means	Bad	In the course of work	Total	% analyzed by class of ways
National roads	44	4	0	0	48	74%
Primary	107	14	4	3	129	78%
Secondary	30	9	6	0	45	57%
Tertiary	21	16	6	1	44	2%
Total	202	45	16	4	267	11%

Another study carried out by ECTA-BTP in 2006 fact the point on the state of the structuring network of the city. This study aimed to work out a multiannual program of maintenance of the priority roadway system of Yaoundé and related to 281 kilometers of «structuring» ways, mainly paved. Three criteria of synthetic qualification of the state of the sections were given for the needs for the study:

· «Good» if degraded surface is lower or equal to 10% of the entire surface of the section;

· «Average» if degraded surface lies between 10 and 30% of the entire surface of the section;

· «Bad» if degraded surface is higher than 30% of the entire surface of the section.

State	Roadway	Dependences of the roadway	Cleansing	Lighting	Indication/safety
Good	75%	34%	42%	32%	7%
Means	17%	15%	11%	2%	1%
Bad	8%	47%	43%	62%	89%
No value	0%	4%	3%	3%	3%
Total	100%	100%	100%	100%	100%

If the state of the roadways is described as «good» in 75% of the cases, the other elements were often recognized «bad», in particular the lighting, the street signs and safety.

It is to note efforts which are made in the direction of the resolution of these various failures in particular through constructions of various penetrating ways and of skirting which will make it possible to better manage the through traffics in the town of Yaoundé.

3.2. The functioning of the transport system

A collective transport system includes three components: vehicles, infrastructures, and techniques of exploitations. Each one of its elements influencing as well on the capacity of this transport system as on its rate per hour which is the number of passengersto transport per hour and direction.

Indeed, the road infrastructure being the support of any road terrestrial displacement, it is possible to optimize and make profitable the functioning of the transport system by improving its characteristics.

In the town of Yaoundé, the average width of the streets (between frontages) is around 20 Meters the roads have an influence going from 6 meters to more than 60 meters (Boulevard of May 20th) of width between frontages. The Table hereafter which gives the distribution of the roads raised according to the number of lanes by directionwatches that only a third of the raised ways thus has 2 to 3 lanes by direction.

In fact, this narrowness of streets observed in the town of Yaoundé can be conceded with the insufficiency of the secondary roadway system; This level of roadway system is essential because it relates to ways which strongly structure the internal exchanges with the perimeter of study (urban space in this case) but also with outside. Today, it is this level of roadway system which is the least readable in the town of Yaoundé. It (secondary roadway system) does not provide correctly its functions in particular for the soft modes and public transport.

· To define characteristics which make it possible to ensure the fluidity and the safety of all the modes of displacements;

· To allow public transport to be powerful and to provide to the cyclists continuous cycle installations.

A hierarchisation of the principal traffic motivations carried out in the town of Yaoundé gives the percentages gathered in the following table

Table8: Distribution of the principal traffic motivations in the town of Yaoundé

Reasons	Numbers	Percentages (%)
Residence - work	3654	20%
Work - residence	2068	12%
Residences - Visits	1437	8%
Work - Work	1270	7%
Residences - Stores (Markets)	886	5%
Visits - residences	754	4%
Residences - businesses	731	4%
Stores (Markets) - Residences	721	4%
Residence - School	692	4%
School - Residence	562	3%
Total	12775	71%
Total investigations	17955

These reasons account for 71% of all the traffic motivations raised at the time of the investigations. The reasons related on the residence and works are most important, those related to the visits, stores and schools follow them of rather far. These data must thus be taken into account in the installation of a powerful roadway network system especially with regard to urban displacements.

2.183.000 vehicleswere counted during the investigations of traffic, that is to say an average of 13.400 vehicles per section of roadway system on which a station of investigation was located. The traffic ranges between 1.500 to 33.400 vehicles by direction on the whole of the surveyed sections. The morning traffic is roughly distributed 60-40 between the two directions, with a maximum traffic of 800 vehicles per hour for the most charged direction. Within the city, the traffic of the vehicles is highest on the network in the north of the roundabout of Nlongkak and at the level of the crossroads of Warda and the Post office. The traffic generally has a radial structure in the town of Yaoundé. It moves mainly towards the center town area, the commercial districts and the administrative buildings. The motor bikes meet especially in periphery of the city. The decree prohibiting the motor bikes taxis in the center of Yaoundé thus seems respected. We observe in particular many displacements in the motor bike in the western part of the city.

Figure 7: Total traffic on the roadway network system structuring town of Yaoundé

The average rate of congestion on the network at the rush hour is of 0,3; knowing that a rate of congestion higher than 1 would mean a saturation of the network. The saturated sections represent 14 kilometers out of the 270 kilometers of the structuring network, that is to say 5% of the linear total.

The proportion of the taxis and the cars in the total traffic is exceptionally high in Yaoundé; Together they account for 91% of the counted traffic. The proportion of the taxis on the sections where counting took place varies from 19% to 72% of the total traffic of the vehicles with an average of 52%. It is a very high figure which proves the insufficiency of the services of public transport per bus and minibus.

With regard to the vehicles used in the installation of a powerful transport system, it would be preferable to have large vehicles which have important capacities such a bus which has a capacity from 60 to 100 places or 270 places for the Bi-articulated buses, against 10 to 20 for the minibuses, 05 for the taxis and finally of 01 place for the motor bikes. These different modes, it is clear, compared to the bus have a highercoefficient occupation time of space per passengers.

From which does it thus come that these various other means of transport (minibus, taxis and motor bikes) make remarkable great strides in the various Cameroonian cities in general and in the town of Yaoundé in particular?

Their rise can be to regard as letting show through a failure, a weakness of the various transport systems undertaken by the public authorities through the country.

The fact of being owner has importance for the people using their car and their motor bike. Nearly a quarter of the questioned population stated not to have the choice between various means of transport, for various reasons such as:

20% of the people investigated declare that they choose the fastest means of the transport; it is particularly true for the motor bikes on the short distances. 13% choose the mode the least expensive, primarily the buses, and 9% seek best comfort in the mode than they chose. The average time of displacements all modes raised by the investigations is 29 minutes. On the other hand the users of the buses have on average 50 minutes of voyage, including waiting, which is clearly a brake to the use of the transport system by bus.

A study of speeds of course by motor bikes and by cars on 05 routes in the town of Yaoundé emphasizes an average rate of travel in the car of 16,5 km/h. The mean velocity of the cars is lower by 3 km/h than that of the motor bikes, because these last circulate more easily than the cars in the zones of strong traffic.

Tableau 10: Results of the investigation of running times (in minutes) (Cars)

	Direction 1			Direction 2			Total
	Length	Time	Speeds	Length	Time	Speeds	Length	Time	Speeds
1	20,6	88,0	14,0	21,1	78,0	16,2	41,7	166,0	15,1
2	18,2	57,0	19,2	18,1	49,0	22,2	36,3	106,0	20,5
3	16,8	59,0	17,1	16,8	67,0	15,0	33,6	126,0	16,0
4	26,0	108,0	14,4	25,9	106,0	14,7	51,9	214,0	14,6
5	22,5	80,0	16,9	22,3	85,0	15,7	44,8	165,0	16,3
Moy	20,8	78,4	16,3	20,8	77,0	16,8	41,7	155,4	16,5

Tableau 11: Results of the investigation of running times (in minutes) (Motor bikes)

	Direction 1			Direction 2			Total
	Length	Time	Speeds	Length	Time	Speeds	Length	Time	Speeds
1	20,6	56,0	22,1	21,1	53,0	23,9	41,7	109,0	23,0
2	18,2	60,0	18,2	18,1	52,0	20,9	36,3	112,0	19,4
3	16,8	57,0	17,7	16,8	57,0	17,7	33,6	114,0	17,7
4	26,0	78,0	20,0	25,9	80,0	19,4	51,9	158,0	19,7
5	22,5	72,0	18,8	22,3	87,0	15,4	44,8	159,0	16,9
Moy	20,8	64,6	19,3	20,8	65,8	19,5	41,7	130,4	19,3

Studies made it possible to model the relationship between the flow and the speed of circulation on a way; they thus make it possible to define and this with a function represented by an ellipse, this relation.

When we places in X-coordinate the flow «Q» and in ordinate practicable speed «V», we notes that to a low flow correspond two very different practicable speeds: one high and the other weak. The corresponding concentration is then inversely proportional to the speed: the higher speed is, the weaker the concentration is.

Figure 9: Theoretical curve of the relation between the flow and speed on a way

The relation between the flow and the speed of circulation establishes that in situation of «hyper congestion» in the lower part of the curve, the increase in the traffic decreases the number of vehicles per hour circulating on the way (numbers of passengers per hour, if we consider only public transport). The important congestions that occur on the main axes of connection centers/periphery in the agglomeration of Yaoundé let think that we are in situation of hyper congestion at the rush hours. The recourse by artisanal transport, majority in the traffic, to vehicles of low capacity involves a loss of capacity of the access roads to the center thing which tends to worsen with the narrowness of the streets observed in the town of Yaoundé.

The resolution of these multiple problems with which is confronted the operation of the transport system in the Cameroonian cities in general and the town of Yaoundé in particular thus passes inevitably by solutions such the urban installation of a urban transport system of mass which will make it possible to reduce the number of vehicles on the ways and thus to reduce the levels of congestion on the various ways components the roadway network system.

Figure 10: Reorganization of the offer of public transport with anUrban Transport System of Mass

It is important to point out the fitting of adequate installations which will have to allow the good installation and the good performance of this urban system transport of mass. We can list

· The installation of certain facility for the joint grid system such the exclusive way which is a way reserved exclusively or not for the circulation of the bus or any other particular transport system such the tram. The installation of this type of way makes it possible to separate the bus for example from the current traffic what contributes to improve its speed and thus its profitability like transport system.

Indeed, Because of weakness of the level of coverture of the urban highway network (paved and in good state) in the Cameroonian cities, to integrate these installation on all the access roads would be utopian and unsuited. In order to be realistic, we recommend an integration of this type of installation on the major axes of the agglomerations. For example, with the configuration of the roadway network structuring the town of Yaoundé as higher presented, it more suitable to integrate this installation (exclusive way for Autobus) on the secondary routes of the city. Thus, this modification of the profile across the primary and secondary roadway system would make it possible the transport system by bus to be better integrated in the city because it would serve the various major axes effectively leading to the various districts of the city and thus would leave the relay to the other modes such the taxi and/or the motor bike the care to continue the service road in the depths. That would make the transport systemby Autobus more effective because it would combine this time speed, comfort and safety.

3.3. Impact in the field of the road safety

The inadequacy of the installation of the roadway system of a city can also have impacts on safety in road.

	Center	Littoral	West	N.O	S.O	South	Adam.	Ea	North	Fa-No.	Total
January	407	21	24	0	5	0	11	6	0	5	479
February	410	0	12	18	12	10	0	3	0	1	476
March	379	0	21	0	10	16	0	5	0	0	431
April	273	0	15	4	5	11	0	5	0	0	313
May	315	0	5	0	18	3	0	2	0	0	343
June	288	179	5	0	6	17	0	4	0	4	503
July	363	210	4	1	9	5	0	6	3	3	604
August	297	12	1	2	9	8	0	10	2	0	341
September	293	178	17	0	16	10	6	0	4	0	524
October	422	63	20	9	17	9	0	3	22	0	565
November	295	171	9	22	34	9	4	8	16	3	571
December	277	160	10	24	29	8	7	7	19	6	547
Total	4019	994	143	80	186	111	17	59	66	22	5697

Table13: Average road accidents per day recorded during the year 2008 in the center region

From these figures, it rises that the physical and material accidents in the area of the center region in general and the in town of Yaoundé are one of the leading causes of mortality (1056 died, 851 cases of accidents fatal) and of the loss of the tangible properties (6844 damaged vehicles).

These accidents, for those which are done following a collision pedestrian/vehicle are the result of the inadequacy of the functions local life and road traffic as higher presented in this memory.

Several factors are thus found to be the source of these multiple traffic accidents.

3.3.1. Humanfactors

The users are the principal responsible of the accidents. The reasons are varied. The imprudence of the driver, the non-observance of the driving code, the lack of control of the vehicle, the excess speed, the catch of alcohol or narcotic products are as many human failures which involve accidents here. One can indicate besides that these the last two factors are surely underestimated, because they are not the subject of detection.

3.3.2. Factor vehicles

The mechanical or technical causes are those which are related to the bad condition of the vehicles, this is due to the absence of maintenance. On this aspect, the Cameroonian government tried to bring a solution by instituting a control of a periodicity determined by category of vehicles, but although there is an obligatory process of technical control of the vehicles regulated by the decree n° 011/A/MINT of February 23rd, 1998, mow is to note that the vehicles often do not have the technical elements of safety complete and that one can circulate in Yaoundé with vehicles with the windshield postpones lack and with defective concerned with safety units. They are mainly the taxis and the minibuses. The strong frequency of controls to which they are subjected does not improve of anything park quality. As this study carried out in the town of Douala shows it and attests it the engineering service of CADCIA, technical control raises the failures related to braking, with the state of the tires, the shock absorbers, the traffic lights, the headlights and the problems of direction. According to the statistics of the approved centers, for the technical visits of car of the town of Yaoundé in particular CADCIA and WCI, on the 150 vehicles received on average per day, 1/3 are returned for this type of failures.

3.3.3. Infrastructural factor

It is the factor on which a local government agency can influence, and by there, influence the human factor, by the control speeds practiced in particular. The user makes a reading of the borrowed way and it adapts its behavior, sometimes in a perfectible way, with the crossed environment. Also one does not arrange a street like a highway, because one does not circulate there in the same way.

The report of the national mission details very well, for a community which arranges the ways, the risks of fight against the accidents in these installations. We have then illustrated this very important point for examples of problems raised in Yaoundé without denying all the completed work for several years and which gives partly satisfaction.

The design of the roads is subjected to standards varying according to the countries. In Cameroun, the standards used are the French standards. When these standards are scrupulously respected and sufficiently explicit, road installations for the users (markings, indication, automatic measurements of deceleration, etc.), they can have a positive incidence on the behaviors. However failures in the technical design can have negative incidences on the behavior of the users, because rather causing additional difficulties in circulation (absence of markings, bad or misses indication of the obstacles, etc.) These failures increase the accident risks of circulation and thus expose more the road users.

Design of the roads in Cameroun present in several cases the defects which contribute to the accident risk. These defects very often result:

· Not taken into account of the agreement between the alignment and the profile longitudinally of the road,

· Not taken into account of the heterogeneity of the traffic, variable speeds, and attractivity of the road,

· Of a design allowing a great disparity with regard to practiced speeds and the types of vehicles.

There exist many accidentogenes places isolated or gathered along the roads. These places often remain without treatment leading thus to other traffic accidents in these same places. With regard to the safety equipment, certain aspects of the design must be followed with a certain attention:

· The material constituting the safety equipment: The originators were sometimes led to the choice of the rigid material equipment such as the concrete (control panels out of concrete, concrete slides, etc.) in order to reduce the maintenance costs of the aforesaid equipment. However, this choice was made with the detriment of safety users, because by privileging the longevity of a control panel by the choice of the concrete like constitutive material, one exposes the vehicles which, in the event of shock with the panel, find themselves seriously damaged (the panel which cannot absorb the shock), and consequently the passengers seriously wounded. That goes in the opposition even to the goal of the safety device which is rather judicious to protect them from the accidents.

· Specifications concerning the safety equipment to be set up: II is not rare that on the works of art built in urban environment, one finds for example parapets having horizontal elements of cross-piece. These elements thus laid out create a scale effect making it possible to the pedestrians (especially with the children) to span the parapets, and this with the danger of their life.

3.3.4. Factors influencing the quality of the road studies

The taking into account of safety in phase of design of the road infrastructures is subjected to certain constraints which put at evil the quality of the studies carried out.

· Budgetary restrictions: The taking into account of safety often imposes an increase in the level of installation of the road (enlarging of the radii of curvature, reduction of the declivities, indication and more important safety equipment, etc.), which creates additional costs thus increasing the financial expenses that the country supports which is most of the time borrower for the projects, and which return occasion consequently the less profitable project.

· The level of priority of safety in the road design: One of the difficulties at present in the realization of the road studies resides in the terms of reference, because those do not impose in a clear and precise way technical constraints related to safety at the Technical Research departments (Study Bureau) and the Companies of realization.

· The dispersion of the made efforts: The intervenants in the road safety are divided in various sectors, but each one carries out by her side the fight against the road insecurity, and thus certain actors go sometimes until being opposed between them by creating problems which harm the good behavior of the studies. The absence of a structure responsible for the road safety charged to coordinate the action of the various protagonists raised previously in the analysis of the organizational device is to be regretted because of inoperationnality of the inter-ministerial committee set up.

· Negligence of the economic impact of the accidents in the evaluation of the projects of road infrastructures

It is necessary to rise that at present, the evaluation of the projects of road infrastructures does not take sufficiently counts of it the profit which the reduction of the number of accidents could generate on a road. Indeed, within the framework of the evaluation, this profit should be put in connection with the cost of the complementary investments to implement to more guarantee safety, this in order to adopt the most advantageous solution, and economically most profitable in the long term. It is about a criterion which could be integrated in a formal way in the appreciation of the road projects.

On the ground, one belongs to installations generating of the behaviors at the risk or having consequences on the gravity of the accidents. These configurations must be proscribed.

The multiplication of the points of conflicts in a crossroads is one of the examples. One finds this design defect in several crossroads of Yaoundé. They are insuperable small islands of form mainly triangular which corresponded to one moment given to an installation, but which was not adapted to the new circulation terms. These small islands, which authorizes to practice without «prohibited direction», call into question the principle of skirting by the line of an obstacle and especially multiply the points of potential conflicts. This is why this configuration differently indicated by «Bennett small island» is proscribed in many countries. One finds this installation with the crossroads EtoaMeki, Coron, Cami-Toyota, MvogMbi, Ngousso where the left-hand turns are not any not simplified.

It should be noted that new installations, if they allow raised speeds, can unfortunately induce accidents with the pedestrians, therefore serious accidents.

Thus the Préfecture exchanger includes/understands it weaving lanes which can encourage at the velocity emission of crossroads and the end of which crossings for pedestrians were marked. This configuration of mixture between characteristics perceived like highway and local life is source of accidents.

Most interesting information of accidentology is information which one can locate. The observation of the behaviors is information source on the non-observance of the rules (in particular that of the indication of tricolor fires or the STOP). For this purpose, dust (as snow in the Scandinavian countries) is also useful for us to distinguish spaces circulated from uncommon spaces in a complex, vast crossroads or in current section of a large artery.

In the same way, the visit on the ground with the agents constatateurs proves to be more enriching and makes it possible for example to detect minor roads which drain a district and whose outlet on the main road is carried out under bad conditions.

The central police station n°4 evokes the sector of Mvan, which is logical because we are at the exit of the city, on one of the most attended arteries. Speeds are increased and the entries and exits of the perilous and non made-up bordering properties. This axis should imperatively be the subject of a thorough study of road safety.

At other places, it is the excess of indication which devalues indication, or rather a bad choice of the mode of priority in crossroads. Thus in a crossroads lately arranged, it was placed a STOP on the file of the left-hand turn, concomitantly with a STOP on the minor road. As this STOP is not respected, because unsuited to this place, they are all the STOP around which is some devalued, as if one could cross any STOP without risk with impunity.

Figure11: Example of a multiplicity of small islands and useless use of a STOP

GENERAL CONCLUSION AND RECOMMANDATIONS

4.1. Recall of the working hypotheses.

The starting point of this work was a rather simple and alleviating statement: the cross sectional profile adopted for a road has an impact on the efficiency of this road in urban environment. In order to be able to bring answers to this question, we have begun researches which have deviate from this starting assumption. Now, the question around which our work was going to articulate was:what is the impact, the importance of the hierarchisation of the highway network in an urban area? Differently summarize, this new assumption, bases of our work would be of knowing what is the importance of the function of the roadway system on its form (width) in urban environment. This new question having been directed by a rather favorable context general that by its rather relevant problems, the second phase at which we had arrived (after the determination of this question) was to carry out a review of the literature which would be articulated around the urban roadway network in particular on its design, its function and its organization.

In this part, through the various articles, documents and theses consulted, we presented the elements on which former work had dwelt too long in particular on the design of the urban roadway system, its various functions and how to organize it in order to make it efficient.

In order to be able to confront our assumption with reality, we should consequently carry out the development, the design of a model. However, at the time of the investigations of data acquisition, it was brought back to us the availability of a document: Elaboration du plan de déplacementUrbains de la ville de Yaoundé, which was worked out in 2010 by the grouping Louis Berger/Beta Consult.

We thus decided to use the data and results of investigations contained in this document and this because of quality (detailed and veracious) of the data and of their relatively recent age (5 years from 2010 to 2015).

This forced us to re-examine the model checking of the assumption that we had fixed ourselves at the beginning. It is thus as in order to be able to conform us to this news gives, we would base on the document referred to above more precisely we would adapt our assumptions has those which were formulated in this document. Thus our new models will relate to:

· The legibility and functionality of the plan of the city and this through data on the quantitative and the qualitative roadway network system of the town of Yaoundé;

· Thefunctioning of the transport system of the city through a model of simulation of traffic.

· The road safety through a simulation of the conditions being able to lead to a confrontation.

Once these various modelsadopted, it was a question for us to pass to the presentation of the results of the investigations on site in order to be able to confirm or to refute our basic hypothesis.

Thus at the end of this exercise, this reveals that the hierarchisation of the roadway network system in an urban environment has indeed a rather important impact on the aforementioned environment.

4.2. Proposals of standard cross sectional profile.

With regard to the various Cameroonian urban centers in general and the town of Yaoundé in particular, we presented proposals for a cross sectional profile depending of the category, and the hierarchy of the way to consider.

4.2.1. For the primary roadway network system:

· of a covered verge, released of any obstacle in order to provide various functions of safety whose width varies between 2 and 3m;

· of band of rolling of which the number is function of the awaited flow; the necessary width is of 3,5 m per lane

· of a central reservation equipped with devices of reserve; its width minimum is of 1 m

i. For the ways supporting traffic in source or direction of the regional capital (national roads forwarding in the city), they should have the characters of a highway; we suggest expressways with 2 X 2 ways: The influence can be limited to 27 meters in order to reduce the costs of acquisition land.

For the penetrating ways used for the exchange between the transit ways and the internal roadway network, it is recommended fast tracks. These roadway systems are used by a large variety of users, which gets an important potential of insecurity. Consequently the top priority will be to separate the users not having the same speed of advance. The configuration of this type of roadway system will have to bring a maximum of safety to the users who borrow it. The standard cross sectional profile of the penetrating ways rises from that from the urban highways and by-pass, with possibility of future extension to 2 X 3 ways (ways of 3,50 meters)

4.2.2. For the secondary roadway network system

This network ensures the principal connections within the urban perimeter. Thus connections between the poles of the urban perimeter on one hand, and with outside on the other hand, are ensured by this category.

Pavements must be arranged on both sides roadway. Their widths are induced by the level of frequentation. The crossings pedestrians must be «in shoe» in order to facilitate displacements of the people with reduced mobility. The presence of a cycle track/exclusive way is essential, and if the widths available allow it, with a clear separation of the lanes. The width of this one must be at least of 2m.

The minimal influence of the minor roads will be of 13 m, of 17 m in the event of adjustment of parking or 25 m for the ways with exclusive way for bus. Certain influences of the town of Yaoundé allow more important widths, and to consider a configuration of parking angle. Off-set zones of stops of public transport will be arranged regularly, preferably at the exits of the crossings to avoid blocking the crossroads. This localization of the stops of public transport also has the advantage not of not too much cutting down the pavements taking into account the broader influences with the crossings. The crossings pedestrians will be also located at the entries and exits of the crossings where it will be arranged central small islands of protection of the crossings.

Figure 14: Modeling of the different types of way for the secondary roadway system

4.2.3. For the tertiary roadway network system

The influence of the way is generally fixed at 11 meters, but could be modified during the studies of preliminary draft according to the constraints of the site. The roadway will thus include two lanes of 3 m, broadsides each by a pavement which can go up to 2,5 meters of width, the gutters included. In the retail parks and near the schools, the pavements will have to be broader, contrary to the residential zones.

In tertiary roadway system and in zone 30 in particular, one can admit a distribution of the widths which makes slow down and which increases the width of roadway to 5 meters, even 4,5 meters when it is about an urban court and the vehicles cross with the step.

ANNEXES

51 the current network of the streets is a whole of developed ramifications goshawks of the main roads of communication.

The 52 great transportation routes were conceived to receive the pedestrians or of cartages, they do not answer the mechanical means of transport today any more.

53 the dimensioning of the streets, from now on inappropriate, is opposed to the use new mechanical speeds and the regular rise of the city.

55 the width of the streets is too insufficient. To seek to widen those is often an operation expensive and besides inoperative.

56 Opposite mechanical speeds, the network of the streets appears irrational, conformity, diversity, flexibility, exactitude lack.

57 Of the layouts sumptuary, working towards representative ends, could or can constitute heavy hindrances to traffic.

58 In many cases, the network of railways (railroads) became, during the urban expansion, a serious obstacle with the urbanization. It locks up districts of dwellings, depriving them of the useful contacts with the vital elements of the city.

59 Of the useful analyzes must be made, on rigorous statistics, of the whole of circulation in the city and its area, work which will raise the beds of circulation and the quality of their flows.

The 60 lanes must be classified according to their nature and built according to the vehicles and their speeds.

The 61 crossings with strong flows will be arranged in circulation continuous by changes of levels.

63 Thestreets must be differentiated according to their destinations: streets of dwellings, streets of walks, streets of transit, ways main.

Extrait de la chartre d'Athènes. Source :d'ARCIER, B. F. (1992). La voirie urbaine : de l'accumulation à la gestion patrimoniale, Thèse de doctorat. Lyon: Université Lumière de Lyon II.

The Consortium Louis Berger/Beta Consult (the Consultant) subscribed on May 4th, 2010 to contract N°047/M/CUY/CPM/10 for the Development of a Plan of Urban Displacements (PDU) of the town of Yaoundé. This contract was approved on May 10th, 2010 by the Delegate of the Government at the Urban Council of Yaoundé (UCY). Its financing will be ensured by funds D registered in the Budget of the Ministry for the Urban Development and Housing of 2009.

· improvement of the urban mobility and the reduction of times of displacements;

· a strategy of regulation of the global offer of public transport and the definition of the principles of exploitation of the grid systems;

· a diagram of organization of transport to the horizon 2020, with programming of the actions necessary to the installation of the PDU at short-term.

· the creation of a clean network of «pedestrians displacements» on the scale of the agglomeration, by the development of an adapted information system strategic plan;

· improvement of the conditions of the urban transit and the management of the breaking bulks (stations, platforms and spaces parking);

· the forecast of installations allowing to dissociate the transport of the other urban activities by in particular imposing a new division of the roadway system in favor of the activities and spaces of leisure, and the walking;

· the examination of the appropriateness of the installation of an organizing authority of transport on the level of the town of Yaoundé in order to ensure the coherence of the sectorial policies and to coordinate the actions of the various actors.

REFERENCES

CERTU. (2008). Fiche n°11 - Sécurité et hiérachie des voies urbaines. Savoir de base en sécurité routière.

CERTU. (2009). Le profil en travers, outil du partage des voiries urbaines. Montpellier.

CORBUSIER, L. (1957). La chartre d'Athènes, Collections Points. Paris: Editions de Minuits.

COSTESEQUE Guillaume. (Avril 2012). ANALYSE ET MODELISATION DU TRAFIC ROUTIER : Passage du microscopique au macroscopique - Mémoire de master MEGA - Génie Civil (éd. Première édition). Marne-la-vallée: Chaire abertis - Ecole des Ponts ParisTech - IFSTTAR.

d'ARCIER, B. F. (1992). La voirie urbaine : de l'accumulation à la gestion patrimoniale, Thèse de doctorat. Lyon: Université Lumière de Lyon II.

Direction départementale des Territoires de l'Ain. (2013, Octobre). Hiérachisation des voies urbaines et modérations des vitesses - Enjeux et méthodologie. Bourg-en-Bresse: Agb Print' .

Dumez, H. (2011). Faire une revue de littérature : pourqoi et comment? Le libellio d'Aegis.

LOUIS BERGER; BETA CONSULT. (2010). Elaboration d'un plan de déplacement urbains de la ville de Yaoundé - Rapport Diagnostic Version Finale. Yaoundé: Communauté Urbaine de Yaoundé.

LOUIS BERGER; BETA CONSULT. (2011). Elaboration d'un plan de déplacement urbains de la ville de Yaoundé - Rapport Final.Yaoundé: Communauté Urbaine de Yaoundé.

MONTEL Marie-Claude, N. C.-E. (2004). Voies urbaine: représentations et attentes des conducteurs de journ de nuit et en soirée. Marne la Vallée: Ifsttar.

NEUFERT, E. (2002). Les éléments des projets de construction 8ème EDITION. Paris: DUNOD.

NOUNDJEU, F. C. (14 au 15 février 2011). Exposé sur les infrastructures. Conférence annuelle des responsables ds services centraux et déconcentrés du MINDUH. Yaoundé.

STRANSKY, V. (1995). Forme et fonction d'un réseau : cas de la voirie urbaine de desserte locale. Paris: Université Paris XII Val de Marne.

* ¹Cross sectional profile seen such as presented in the general introduction of the present document

* ² Abstraction is made on the economic constraints due to the cost of the project. In this part, the stress is laid on the interference with the bordering frame of life.

* ³As underlined at the beginning of this review of the literature, this research wants to be to be corrélationnelle because having for goal to discover or establish the existence of a relation between two common aspects of the urban roadway system: the gauge of a way and its output

* ⁴ Indeed, there exist classically microscopic models and the macroscopic models of study of traffic. The first endeavor to model the road traffic by individual evolution of each vehicle. In this model, the dynamics of the vehicle is given by a law of continuation and the speed of a vehicle is directly function of the distance which separates it from the vehicle right in front of him, modulo a time lag, which is the reaction time of the driver. On the largest scale (called macroscopic scale), the simplest model used is the hydrodynamic model of traffic, which supposes that the density of vehicle satisfies a law of conservation. Here the speed of the vehicles is supposed to be a function of the density of vehicles.

* ⁵By the consultant at the time of the realization of the investigations necessary to the development of the diagnosis of the town of Yaounde or by us even for a possible investigation the purpose of which would be to confirm or to dispute a data or information provided by the Plan of Urban Displacements of the town of Yaounde.