This pilot study was undertaken to investigate whether presently available methods were capable of generating useful information on the relative contribution of microtexture and macrotexture to stopping distance at different speeds. All trials were conducted using the same late model Holden Commodore Station Wagon fitted with anti-lock braking (ABS), a Global Positioning System (GPS), an accelerometer and a computer. Testing was carried out at four sites with different combinations of macrotexture and skid resistance. Data were analysed using a full factorial Analysis of Variance (ANOVA) design., i.e. four levels of site x four levels of speed x two levels of conditions, with five replications at each site. Significant effects were found for all speed variables, all two way interactions and the three way interaction. However, it was clear that by far the largest effect was speed, based on the mean squares and the Partial Eta Squared statistic. The next largest effect was the three way site x speed x condition interaction, which is probably due to the large increases in stopping distance in wet conditions at site 3, which only occurred at higher speeds. Site 3 had low macrotexture and was the only site to have low skid resistance. It may have been possible to obtain better combinations of skid resistance and macrotexture for testing purposes if the minimum length specified for sites (300 metres) had been shorter. The test results suggest that 80 metres of road with consistent surface characteristic would be sufficient. Further investigation of the relation between crash occurrence and road surface characteristics, taking into account geometric characteristics and travel would seem to be the most productive direction for the immediate future.
Type: Research and Analysis Report
Sub Type: Consultant Report
Author(s): Peter Cairney and Anthony Germanchev, ARRB Consulting
ISBN: 0 642 255296
ISSN: 1445 4467
Publication Date: 06/04/06