What are the characteristics of an ideal pavement ?

 There are four characteristics which are considered crucial for an ideal pavement surface. They are 

  1. friction
  2. unevenness
  3. light reflection
  4. drainage
Friction
  As we know, friction is essential to move any body. whether it is human or a particle or a vehicle, they all need frictional force to move forward.
  Thus, friction between wheel and pavement is an essential consideration in designing pavement surface. It affects the acceleration and deceleration ability of vehicle. If sufficient friction force is not generated between the surface and wheels, it may cause skidding and slipping.

  • Skidding happens when the path traveled along the road surface is more than the circumferential movement of the wheels. Ex.- when we applied brake while driving bicycle, the wheels slide without revolving. It is the phenomena of skidding.
  • Slipping occurs when the wheel revolves more than the corresponding longitudinal movement along the road. Ex.- when the vehicle gets stuck in the mud, its tyre revolves at same position without moving forward. It is the phenomena of slipping.
The friction force that develops between the wheel and the pavement depends upon many factors like type of the pavement, condition of the pavement, condition of tyre, and load of the vehicle.
   As per I.R.C. recommendation, the co-efficient of  longitudinal friction should be 0.35-0.4 depending upon the speed and coefficient of lateral friction should be taken as 0.15.

Unevenness
   It is also essential to have an even surface for safe and comfortable driving. But it is not practically possible. Even if a pavement is constructed in well manner by using high quality materials, there is possibility to develop unevenness due to pavement failures.
  So, an unevenness index of less than 1500mm/km is considered as good. It means the cumulative vertical undulations of 1500 mm in 1 km of horizontal length is allowable.

   Unevenness affects the vehicle operating cost, speed, riding comfort, safety, fuel consumption and wear and tear of tyres.

Light reflection
   Light reflection property is also a crucial factor for an ideal pavement surface. The road should be visible at night as well as not glare in the day.

  • white roads have good visibility at night but cause glare during day time.
  • black road has no glare during day but has poor visibility at night.
  • concrete roads has better visibility and less glare.
Drainage
   The pavement surface should be fully impermeable so that seepage of water into pavement layers does not take place. Both the geometry and texture of pavement surface should be help in draining out the water from the surface in less time.


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