Spot Speed Analysis on Urban Roads in Riyadh

Nearly 42 percent of traffic accidents on urban roads in Riyadh, the capital of Saudi Arabia, were attributed to speeding. Compared to U.S. data, this developing country has 4.5 times more accidents due to speed. In this study, spot speed data were analyzed using data collected at 13 urban roadway sections in Riyadh. Five of the study sites were freeway sections, and eight were arterial sections. Speed characteristics, including mean, variance, and 85th percentile, were investigated. The study found that obtaining the 85th speed percentile from regression modeling gives much better estimates than those from the normal approximation model. Driver noncompliance with the posted speed limit was clearly shown. At some sites, more than 90 percent of motorists were exceeding the speed limit, indicating that much more active speed limit enforcement is needed.