Examining the Impacts of Portable Changeable Message Signs on Drivers\u27 Speed Characteristics: A Driving Simulator Study

Using a driving simulator (DS), this paper analyzes the speeding behavior of drivers impacted by four different messages displayed on portable changeable message signs (PCMS) placed upstream from a construction zone on an interstate highway in Missouri. The four PCMS placed sequentially replicated the Missouri work zone and participants evaluated the messages displayed in a DS. The effects on drivers’ speed as a result of these messages were analyzed at eight locations, 1000 ft. before and after each PCMS. Five different scenarios (0-4) were simulated; control scenario set up with static signs. In Scenario 1, “Caution Work Zone Ahead: Reduce Speed Ahead” was displayed on the PCMS. Scenario 2 utilized (MS-2), “Speed Ahead 30 mph/2 mins to end of Work Zone.” Scenario 3 tested “Prepare to stop/2 mins to end of Work Zone”, and Scenario 4 deployed “Prepare to stop/Stopped Traffic Ahead.” Scenarios 1-4 were compared to the control scenario; Scenario 4 had the highest speed reduction, followed by Scenario 3, Scenario 2, and Scenario 1. The 85th 13 percentile speeds in the work zone closely matched with the displayed speed for MS-2. A significant reduction in speed was found on the eighth interval as it was placed before the start of the lane closure. Results from a drivers’ survey conducted after the DS experiment, indicated that MS-2 was the preferred message as it displayed a specific speed for the participants to follow. The results from the survey reinforced that PCMS were effective in reducing the speeds of the drivers