| This research examines the effectiveness of advisory variable speed limit (VSL) and advisory variable message sign (VMS) messaging on reducing traffic speeds during inclement weather conditions. Regulatory variable speed limit infrastructure is costly to install, whereas advisory messaging enables state transportation departments to utilize existing infrastructure in an effort to slow traffic during winter storms and improve safety. This study utilized roadway sensor data in southern New Hampshire, roadway grip data obtained from a Road and Weather Information System (RWIS) station located in Derry, New Hampshire, and New Hampshire Department of Transportation (NHDOT) winter weather logs obtained from the Transportation Management Center (TMC). The data were used to determine the impact the advisory messages had on reducing traffic speeds as compared to the impact roadway grip has on speed reduction.;Overall, this analysis indicates that, while drivers do adjust their rates of speed based on the roadway grip value, the presence of both prescriptive and descriptive messages appears to cause them to reduce their rate of speed even further than they otherwise would, especially during storm events with large amounts of accumulating precipitation. Speed reductions were found to be more significant while prescriptive messages were displayed, although significant reductions in speed were also noted while descriptive messages were displayed. After controlling for the slowdown caused by a reduction in roadway grip, it was determined that the presence of prescriptive messages reduces the mean speed by 9.5 mph, and descriptive messages reduces the speed by 2.5 mph. |
