Design Of Road Pavements

INTRODUCTION
The importance of road to life and activities can not be overemphasized. Roads have important role to play in the transportation system of the country. Good transportation system through the pavement design has in the recent years provide to be of much significance commercially and otherwise history testifies that the provision of roadways is necessary to draw a country out of a state of uncivilization, but that civilization is not attained until good road network between neigbours is made so easy that the local difference which brench narrowness is minimized.
However this project has been designed strictly to modern design standards e.g. ASSHO method and it centers on the route survey and pavement design of the road to meet with the present day effective services.
Moreover, this project work could really sever as a future guide in making a new rural road, down to industrial layout to connect mass comm..
Therefore being in a school environment a good transportation system will improve the healthy studying condition of the new road pavement and maintenance of the existing one.

1.1 RELEVANCE OF PROJECT
The roadway linking Federal Secretariat industrial centre and Mass Communication Department is an earth road of about 0.620km in length whose origin can be traced back to the origin of the I.M.T campus III environment.
The project work has its relevance centered on the general design of a roadway which will link federal secretariat, industrial centre and Mass communication Department in order to ensure a hitch free traffic especially to the lecturer, visitors and students making use of that industrial centres
However the improvement of this roadway would grieve the students and lecturers the service of belonging as it gives easier access to masscom. Department.

1.2 SITE INSPECTION
This project site which is the roadway linking Federal Secretariat industrial centre and Mass Communication Department was inspected to ascertain its location and the present state of the road. It was vividly observed that the area was a dusty roadway throughout its length and had been graded without siderains, spanning about 620m length with the width of 85m.
To obtain these information, a preliminary survey was carried out which also helped to ascertain the geological and soil conditions likely intervals forming the chainages to be referred to until the construction id\s brought to a completion.

1.3 EVALUATION OF ROAD NETWORK W NIGERIA
There are three types of roads in Nigeria
– Grade I: Surface dressed road
– Grade II: laterite on natural soil road
– Grade III road on nature soil
Road, which were built earlier in Nigeria, were built as grade III roads, which consist of roads built on level earth. This grace of road was subsequently improved to grade II roads, which comprises of stone laterite on soil and on general surface roads.
Ultimately, the road was improved to grade I which is laterite road with good surfacing. The surfacing is either asphalted concrete for flexible pavement (in this project work flexible pavement will be considered).
The progressive method of road construction produced very durable roads but because of this rapid growth of traffic on the grade I and II this method of road construction was discontinued and surface dressed roads were built.
Road development receive a set back due to the development of railway in the country between 1895 and 1910 but was only revitalized early 1960when highways were built to connect various party of the country. Today, there is virtually on state capital (if not local government area headquarter) that is not linked directly by a highway.

1.4 MOTOR VEHICLE CHARACTERISTICS THAT AFFECT ROAD DESIGN DATA
In design of road, the current physical characteristics of ehicle in use and the anticipated future improvement in se are all essential. These vehicles are evaluated in terms f a standard vehicle known a design vehicle. The design data for a road stretch include: aix load, axle space, overall length, eight and width of the design vehicle.
1. Length: The length of the vehicle will affect the extra widening at curves and minimum turning radius the passing sight distance the road capacity and parking facilities for example 12m are recommended for a single unit truck while 20m (19:812m) for Troilus
2. Width: The width of the vehicle will affect the lane width the width of shoulders and the width of parking spaces. AASHO recommends a maximum width of 2.59m.
3. Height: The height of the vehicle will affect the overall height distance provided under structure such as: bridges, overhead bridges electric services lines etc. the maximum height for vehicle should not be more than 4m.
4. Weight: The weight of vehicles affects the thickness of the pavement, ruling and limiting gradient and design of bridges.
5. speed: vehicle affects horizontal and vertical alignment design elevation limiting radius, signal distances, width of pavement on straight and curves for the purpose of this project a design speed of 30km/n is been considered. He design speed is the maximum speed maintainable throughout the journey with compatible safely and comfort)

1.5 DRIVER AND THEIR CHARACTERISTICS
A driver could be a vehicle rive, cyclist or pedestrian. There are no average drivers as the capabilities of a driver changes under such effects as fatigue ,frustration, monotony and alcohol. Much speed is the primary cause of accident.
Drivers have different visual perception capabilities to tract promptly to conditions requiring positive action
The major driver characteristics considered are:
1. Reaction time: this is the period of time, which elapses from the period the eye of a driver registers a sene to the time muscular reaction occurs.
2. perception time: this is the period of the much elapses before reaction time begins. AASHO recommends combined reaction plus perception time tobe2.5 sec and can be taken as 3 sec in complex situations.

1.6 RECONNAISSANCE SURVEY
This is a quick type of surveyor rapid examination of the ground and its adjacent natural features usually made with out survey instruments to limit the alternate route in terms of cost tone or two.
In the cause of this project, there reconnaissance survey was carried out in order to obtain a first hand view of the road by walking through the length of the road thereby having a clear picture of the entire roadway. This is also helped in determining the most suitable way of carrying out the project economically in time and energy. During the process of reconnaissance, survey stations were chosen and marked.

1.6.1 CHAIN SURVEY
The method adopted in marking linear measurement is the linear measurement in which a employed in making a direct measurement is dependent of the degree of accuracy required. However in cause of this project, accuracy in measurement was maintained to a moderate level. Obstacle such as rough ground, pedestrian traffic and motor cycle traffic were avoided as much as possible.

1.6.2 STATION MARKING
The survey stations were marked in such way that will fulfill the following requirement.
a. The stations where to be easily and quickly found during survey operations.
b. They were to be fairly permanent so that pedestrians will not easily remove them.
c. They were marked using bottle tops and nails at the center line of the road for easy location of these stations, temporary stations were established at the edge of the road using wooden pegs.

1.7 FACTORS AFFECTING THE CHOICE OF STATION
These factors include the following
1. Easy meaning condition: stations are to be chosen in such a way as to avoid obstructs during draining or tapping exercise.
2. Inter-visibility: stations are to be chosen and placed in such a manner that no station on struts the line of sight of another stations. This was considered for both traversing and leveling.
3. Traversing at close distance should be avoided in order to avoid angular errors being introduced if targets at short range are not properly bisected.