2. Unevenness
Presence of underation or unevenness of pavement surface.

The unevenness result in:

  • Increase fatigue

  • Reduce speed

  • Increase fuel consumption

  • Increase wear & tear of wheels

  • Increase chance of accidents

  • The unevenness of pavement is measured with the help of equipment BUMP INTEGRATOR (BI) in terms of unevenness index which is the cumulative measure of vertical modulator of pavement surface recorded per unit design of the road.                   

The different value of unevenness on indian roads and corresponding serviceability is as follow:












  • NOTEInternationally the riding quality of pavement surface qualified in terms of roughness & is expressed as “INTERNATIONAL ROUGHNESS INDEX” (IRI) having unit of (m/km) it can also be selected with unevenness index as follow

  • Bump Integrator (BI) Bump Integrators or Rough meters are superior to that of conventional feeler gauges or wedges because of the following reasons: 

  •  Quick measuring process 

  •  Ideal for long stretches It is available in the form of single wheeled trailer, these recorders give quantitative integrated evaluation of surface irregularities on an electronic counter. 

  • The features of this are mentioned below:

  •  Accessories: 

  •  Trailer of single wheel with a pneumatic tires mounted on a chassis 

 Penal board fitted with 2 sets of electronic counters (for counting the unevenness index value) Specifications: 

  • Operating speed: 30 ±½ Km/Hr 

  • Towing operation: By a vehicle, usually a jeep Maintaining the speed of 32 km/hr is a difficult task in using and working with a bump integrator, especially for small stretches. In order to overcome this limitation alternative approaches are needed to save time, money and reduce the laborious work. As a result the following relations are used. The empirical relationship between BI and IRI is given below: 

  • By CRRI IRI=(BI/720) 

  • By M.A Cundill IRI=(1+1.05(BI/1000)

  • For semi dense bituminous concrete, the conditions are Good<2500, (95km/hr) Average (2500-3000), (65km/hr-95km/hr) Poor>3500, (<65km/hr) 

Unevenness Depends on Following Factors

  1. Improper compaction

  2. Use of improper compaction method

  3. Use of inferior quality material

  4. Improper surface of subsurface drainage

  5. Poor maintenance of pavement surface