The roughness of road surface is an important measure for road surface condition evaluation and a key factor in determining its riding quality. As such, road roughness measurement has received a considerable attention from road and airport agencies / authorities as it affects the safety of the individuals using roads, riding quality of the roadway, the pavement loading and the vehicle operating cost. In India, riding quality is largely being measured by one of the response type instruments called Bump Integrator (BI), which are either towed type / Fifth Wheel mounted on the vehicle itself. The measurements obtained from BI must be correlated to the standard roughness scale by calibration. For calibration of BI, the first class profilometre called Dipstick is commonly used and the relation equation UI = 630 (IRI)1.12 is applied for correlation with BI values, where UI = Bump Integrator Roughness in mm / km while IRI = International Roughness Index in m/km. Based on the testing of a large number of Fifth Wheel BIs, it has been found that the percentage error of calibrated roughness w.r.t. reference roughness is very high particularly for lower roughness levels by using the above standard relation equation. In this paper, an improved relation equation is proposed for the calibration of BIs in Indian conditions. Using the proposed relation equation, better / improved relations have been derived by reducing the percentage error of calibrated roughness w.r.t. reference roughness.
Lalita Jangpangi, H.Lokeshwar and Y.C.Tewari
CSIR-Central Road Research Institute (CRRI)