Dual-Advisory Speed Signing on Freeway-to-Freeway Connectors in Texas

Abstract

This project recognizes the disparity in the relationship between truck and passenger car speeds and current advisory speed-signing practices. The results of this project provide a mechanism that traffic engineers may use to provide enhanced differential warning to trucks and passenger vehicles at freeway connector ramps. The strong evidence of a significant differential between the speeds that cars and heavy trucks can comfortably and safely traverse freeway connector ramps or loops revealed a need for further research. This research would investigate current advisory speed-signing practices and examine whether a dual-advisory speed-signing scheme, one that provides different recommended advisory speeds for trucks and passenger vehicles, can safely address this differential. On the basis of the results of the analysis of average and 85th-percentile speeds at the midpoint of each study curve, the dual-advisory warning signs had a positive impact on reducing speeds at the point of curvature on the curve and had an accompanying reduction in speed-related crashes at the study sites, or both.