Effectiveness of Variable Message Signs on Utah Roadways

This paper presents the findings of a dual-approach research study conducted for the Utah Department of Transportation to evaluate the effectiveness of variable message sign (VMS) treatments on Utah roadways. The study aimed to determine the impact of VMS treatments on mobility and safety for Utah’s unique road conditions and configurations. Two primary analyses were performed: a diversion rate analysis to assess the effectiveness of VMS messages on Utah freeways during incidents and a weather analysis to evaluate the effectiveness of VMS messages on driver speeds in Utah canyons during winter weather. The findings of the diversion rate analysis indicate that the activation of VMS messages during crash incidents increased diversion rates by 18 percent. The weather analysis showed that the activation of VMS messages warning drivers to slow down due to inclement weather conditions increased driver speeds by 0.23 mph (0.37 kph) during weather conditions, which was statistically significant, but holds little practical significance. The methodologies and findings of this study will assist departments of transportation and other interested parties in developing their VMS policies to more effectively influence driver behaviors.