Impact of the type of the cross sectional profile on urban zones road

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.

As follows:

· 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.

* 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