Current Attitudes among Transportation Professionals with Respect to the Setting of Posted Speed Limits

Abstract

A recent survey conducted by the National Committee on Uniform Traffic Control Devices Task Force explored current and potential approaches to the setting of posted speed limits. The survey was distributed in the spring of 2018 and gathered 740 responses. The survey found that many states and local agencies have their own laws or criteria for the setting of speed limits (many are very detailed). Professionals who perform posted speed limit studies rarely only use the 85th percentile speed. It is clear from the survey that analysts who establish speed zones utilize many factors beyond the 85th percentile in their studies, including the context, that is, where the street is and what function it serves. The use of the 85th percentile for rural roads or interstate/freeways is different from urban streets (on urban streets, the 85th percentile plays a less significant role). The industry knowledge and use of USLIMITS2 are very limited. USLIMITS2 is a web-based tool designed to help practitioners set speed limits and is maintained by the Federal Highway Administration. Setting of reasonable speed zones requires consideration of many factors that are currently not well defined in the Manual on Uniform Traffic Control Devices (MUTCD). These factors are best defined as part of national guidance/research or local policy documents and do not need to be defined in the MUTCD as they can involve state/local interpretation.