New Zealand's road network uses pavement types of widely differing properties, ranging from very smooth asphaltic concrete to coarse chipseal surfaces having macrotexture levels not often found elsewhere in the world. A research programme was undertaken between 1988 and 1995 to investigate the effect of surface texture of a road on the rolling resistance of a typical tyre/car combination. Data available in the international literature was reviewed during 1994–95 following analysis of the New Zealand results.
A comparison of the coastdown and steady state torque methods established that the latter was more suitable for measuring vehicle drag forces on public roads. Accordingly, it was used to obtain static and dynamic rolling resistance coefficients for 12 different road surfaces having approximately the same roughness, but with macrotexture depths which ranged from 0.6 mm to 2.7 mm.
The coarsest textured surface investigated had a static component of rolling resistance that was 55% greater than that of the smoothest. Regression analyses established that the static component of rolling resistance is strongly correlated to surface profile wavelengths between 0.5 mm and 50 mm. In addition, a limited investigation of rolling resistance changes related to road surface age-traffic loading effect was conducted for a porous friction course surface. The traffic loading dependency of rolling resistance was shown to be interdependent with the macrotexture and roughness progression characteristics of the road surfacing type.
Keywords: Chipseal, coastdown, cost, fuel, fuel consumption, macrotexture, New Zealand, road/tyre interaction, roads, rolling resistance, surface texture, texture, torque, tyres, vehicles, vehicle operation costs, VOC