Assessing tribal roads with improperly designated speed limits: A case study of Wyoming

ABSTRACT

Establishing appropriate speed limits is a critical issue in transportation engineering. This study entailed the examination of speed limits of rural tribal roads in Wyoming<apos;>s Wind River Indian Reservation that were set below reasonable levels. In particular, the roads’ 85^th percentile speeds were modeled using quantile regression and their average speeds were modeled using random parameters, or mixed, Tobit regression. The risks of encountering drivers exceeding the speed limits were modeled using mixed logistic regression while the speed variances were modeled using mixed Tobit regression. The aforementioned outcomes were modeled as functions of traffic and roadway parameters. According to the results, it was concluded that the outcomes were influenced by the shoulder width, posted speed limit, and difference between the posted speed limit and the appropriate speed limit recommended by the USLIMITS2 expert system of the Federal Highway Administration. As such, recommendations were made concerning the roads under study.

KEYWORDS:

• Speed limits
• speed limit compliance
• tribal roads
• random parameters

Acknowledgments

The authors would like to thank the Wyoming Department of Transportation for providing part of this study’s data and the Wind River Indian Reservation for its permission to conduct the spot speed studies in its territory. All opinions are solely of the authors. The subject matter, all figures, tables, and equations, not previously copyrighted by outside sources, are copyrighted by the Wyoming Department of Transportation, the State of Wyoming, and the University of Wyoming. All rights reserved copyrighting in 2022.

Disclosure Statement

There are no potential conflicts of interest.