BACKGROUND

NCHRP Research Results Digest 318: An Expert System for Recommending Speed Limits in Speed Zones (2006) resulted in the deployment of the USLIMITS2. USLIMITS2, hosted by the Federal Highway Administration, employs a decision algorithm to advise the user of the recommended speed limit for the specific road section of interest. The existing algorithm focuses primarily on operating speeds (85^th percentile speed, 50^th percentile speed) and other variables entered by the user to determine the recommended speed limit. USLIMITS2 was updated in early 2018 to improve usability, but the decision algorithm has not been updated since 2006. New research should refine the decision rules of the algorithm and develop the next generation of USLIMITS2.

OBJECTIVES

The objectives of this research are to (1) determine what updates are needed for the USLIMITS2 decision algorithm to establish safe, credible, and enforceable speed limits for a variety of facility types and contexts, including high, moderate, and low speed facilities that serve all roadway users; (2) update the algorithm and conduct user testing; (3) identify and incorporate potential enhancements that will increase the user base; and (4) develop an implementation and training plan.

STATUS

To be competed under NCHRP 03-139A.