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Testing Effects of Warning Messages and Variable Speed Limits on Driver Behavior Using Driving Simulator

This study examines the effect of warning messages and variable speed limits (VSLs) on driver speed. Using a driving simulator, the study observed behavior of 86 participants who drove a 5-mi section of a freeway. On this freeway, three types of warning message were displayed in variable message signs (VMSs) to warn of an impending speed change. Drivers were typically required to reduce speed first and then increase speed according to VSLs. It was found that when warning messages and VSLs were displayed, participants generally drove at uniform speed and their variation in speed along the section was reduced. Statistical analysis using a binary logit model revealed that there exist correlations of driver speed changes and compliance with speed limits at successive locations of VMS. Findings of the simulator experiment suggest that warning messages and VSLs are beneficial in reducing speed variation and removing congestion. These effects of warning messages and VSLs can potentially reduce crash risk and improve efficiency on freeways.