The pavement of the road should have a sufficient thickness so that it can properly distribute stresses into the subgrade soil which are generated due to heavy loads of moving vehicles.
The road pavement should be more durable and required less maintenance.
It should be structurally strong and stable so that it can efficiently take the loads without failure that are imposed on it.
The road pavement should have an adequate coefficient of friction to prevent the skidding of the vehicles.
The road pavement should be smooth enough to provide comfort to the drivers even at the high speed.
The pavement should have resistance to water absorption and have very little porosity so that the subgrade layers of the soil will be protected and prevent settlement of road pavement.
The road pavement should be dustproof and ensure that there will be less generation of noise when vehicles are moving from the surface of the road pavement.
The road pavement should be economical and easy to construct.
It should have good visibility at night at riding from the road surface should be smooth and comfortable.
The road pavement should be suitable for all types of traffic and it should not develop any corrugations.
Flexible pavements: Those which are surfaced with bituminous (or asphalt) materials. These types of pavements are called “flexible” since the total pavement structure “bends” or “deflects” due to traffic loads.
Rigid pavements: Those which are surfaced with portland cement concrete (PCC). These types of pavements are called “rigid” because they are substantially stiffer than flexible pavements due to PCC's high stiffness.
Surface Course: The layer in contact with traffic loads. It provides characteristics such as friction, smoothness, noise control, rut resistance, and drainage. In addition, it prevents entrance of surface water into the underlying base, subbase and subgrade. This top structural layer of material is sometimes subdivided into two layers: the wearing course (top) and intermediate/binder course (bottom).
Base Course: The layer immediately beneath the surface course. It provides additional load distribution and contributes to drainage and frost resistance. Base courses are usually constructed out of aggregate or AC.
Subbase Course: The layer between the base course and subgrade. It functions primarily as structural support but it can also (1) minimize the intrusion of fines from the subgrade into the pavement structure, (2) improve drainage and (3) minimize frost action damage. The subbase generally consists of lower quality materials than the base course but better than the subgrade soils. A subbase course is not always needed or used.