Driver-speed behaviour on approaching and traversing yellow bar carriageway markings was studied to ascertain the effectiveness of the markings in reducing vehicle speeds. 8 sites throughout Peninsular Malaysia were selected for the study; each site being of different geometric layout and featuring different types of road hazards. With the exception of 2 of the sites, the study was carried out in 3 stages; i.e. when there were no markings at the sites, when there were markings at the sites made with roadline paint and finally, when there markings at the sites made with thermoplastic material. Spot speed measurements were performed by using "radar guns" at 3 or 4 stations located on the approach to, and at various points the approach to, and at various points along a set of yellow bar carriageway markings. Over 120,000 speed measurements were obtained from a total of 31 stations and the results were analyzed using statistical computer software. Vehicle-speed profiles were plotted from the results obtained and speed-change patterns were observed for mean and 85%ile speeds. It was found that, on the whole, yellow bar carriageway markings caused a more stable driver speed reduction pattern before reaching a hazard. Carriageway marking made with thermoplastic materials have been found to be more effective than the markings made with normal paint. However, it should not be a substitute to installing regular warning signs or as a compensation for inadequate sight distance because yellow bar carriageway markings are only effective on an approach to a visible hazard such as a junction or a narrow bridge. (A)
Abstract