Citation

Al-Ghamdi AS. Transp. Res. Rec. 2006; 1969: 1-9.

Affiliation

College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia

Copyright

(Copyright © 2006, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The current study tackles three aspects of the speeding problem. First, the magnitude of the problem for driver compliance is assessed by a comparison of the 85th percentile speed with the posted speed limit. The second aspect deals with selected speed limits at study sites, and models for estimating these percentiles are suggested. Examining the effect of automated speed enforcement with speed radar cameras and the presence of police cars was the third aspect. A sample of slightly more than 69,000 spot-speed observations was gathered from 41 sites (14 freeways, 22 arterials, and 5 residential streets) during 2003 in Riyadh, the capital of Saudi Arabia, and in Buraidah, a small city about 300 km north of Riyadh. Analysis showed that the study sites were suffering from a tremendous speed problem. Although the problem could be blamed in part on inappropriate selection of speed limits, the speeding trends disclosed that drivers overall tend to exceed the posted limit by a great amount. The proportions of motorists with 85th percentile speeds over the speed limit are 10%, 88%, and 100% on freeways, arterials, and residential streets, respectively. A primary concern is the relatively high speeds observed on residential streets. Although the speed limit on such streets does not exceed 40 km/h, the observed 85th percentiles were all more than 55 km/h; this highlights the speeding issue on these neighborhood streets, where pedestrian activities are prevalent. The study found that both enforcement methods, namely, speed radar cameras and police car presence, appeared effective and led to a reduction of mean speed by at least 10 km/h.