Evaluation Of Longitudinal Evenness Of A Newly Constructed Road Section: A Detailed Study Of Different Evenness Measurements

The requirements for longitudinal evenness of newly constructed road surfaces in Belgium are expressed in the “Evenness Coefficient” (EC) defined as half of the surface between the profile as obtained from measurements with the “Analyseur de Profil en Long” (APL) and a curve representing the “ideal profile” calculated by a sliding average method. Requirements can be expressed in the gap height measured with the “three-metre straightedge” (TMS) but the acceptance of road works is often based on APL data. When requirements are not matched, the contractor must improve the longitudinal evenness after road works completion. Contractors and road administrations want to exploit APL data fully. This contribution discusses the finesses of longitudinal evenness measurements using APL, EC and TMS. A case study illustrates to what extend the APL data can be exploited. A road section with high unevenness was investigated by APL and TMS, and the geometrical unevenness of the road surface was measured point-wise by elevation measurements in the wheel paths on 8 sub-sections of the road. The case will confirm that a theoretical estimate of TMS gap height from APL data is realistic and will show rare influence of crossfall variation on the APL.