Citation

Russo BJ, Savolainen PT, Gates TJ, Kay JJ, Frazier S. Traffic Injury Prev. 2017; 18(5): 521-527.

Affiliation

Department of Civil and Environmental Engineering, Wayne State University, 5050 Anthony Wayne Drive, EDC 0504.01 , Detroit , MI 48202 . Email: dy2835@wayne.edu.

Copyright

(Copyright © 2017, Informa - Taylor and Francis Group)

DOI

10.1080/15389588.2016.1261123

PMID

27893283

Abstract

OBJECTIVE: Although a considerable amount of prior research has investigated the impacts of speed limits on traffic safety and operations, much of this research, and nearly all of the research related to differential speed limits, has been specific to limited access freeways. The unique safety and operational issues on highways without access control creates difficulty relating the conclusions from prior freeway-related speed limit research to two-lane highways, particularly research on differential limits due to passing limitations and subsequent queuing. Therefore, the objective of this study was to assess differences in driver speed selection with respect to the posted speed limit on rural two-lane highways, with a particular emphasis on the differences between uniform and differential speed limits.

METHODS: Data were collected from nearly 59,000 vehicles across 320 sites in Montana and four neighboring states. Differences in mean speeds, 85(th) percentile speeds, and the standard deviation in speeds for free-flowing vehicles were examined across these sites using ordinary least squares regression models.

RESULTS: Ultimately, the results of the analysis show that the mean speed, 85(th) percentile speed, and variability in travel speeds for free-flowing vehicles on two-lane highways are generally lower at locations with uniform 65 mph speed limits, compared to locations with differential limits of 70 mph for cars and 60 mph for trucks.

CONCLUSIONS: In addition to posted speed limits, several site characteristics were shown to influence speed selection including shoulder widths, frequency of horizontal curves, percent of the segment that included no-passing zones, and hourly volumes. Differences in vehicle speed characteristics were also observed between states, indicating speed selection may also be influenced by local factors, such as driver population or enforcement.

Language: en