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

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.

Table2: Indicators of roadway cover of Yaoundé                    

Indicator	Yaounde (total network)	Yaounde (covered network)	Developing country	Developed countries
Mètres/1000 inhabitants	1200	350	150 - 3000	530 - 10000
Meters/hectares	90 - 120	26 - 35	40 - 220	60 - 320

Source : PDU Yaoundé

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 network of 166 km of primary roadways system, of which 159 km are paved;

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

· ATertiaryroadway network, of which 478 km of ways are paved.

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

Classifyroadway system	Total (in km)	% of the total	Paved (km)	% Paved by Class
National roads	65	3%	61	94%
Primary	166	7%	159	96%
Secondary	78	3%	57	73%
Tertiary	2.227	88%	478	21%
Total	2 536	100%	755	30%

Source : PDU

Figure 6: Repartition of the highway network system 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 grid of the network;

· 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.

So, an urban space well organized must emphasize

· 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.

Table4: Distribution of the traffics in the town of Yaoundé

	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%

Source : PDU

3,9%

0,4%

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.

The results of this analysis are deferred in the table hereafter.

Table6: State of the priority ways of Yaoundé in 2006

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%

Source : PDU

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.