Evaluation of Digital Speed Limit Signs in Work Zones

Digital Speed Limit signs (DSLs) have been implemented in a restricted number of Michigan Department of Transportation (MDOT) freeway work zone locations with 60/45 (mph) “WHERE WORKERS PRESENT” (WWP) speed limits. DSLs allow for the speed limit to be displayed on a digital panel, which may be modified based on worker presence at the location, providing an advantage over the traditional 60/45 WWP signs by removing the ambiguity regarding the speed limit in place at that time and location. Preliminary testing of the DSLs has identified challenges related to the manual changing of the displayed speed limit, such as signs being left in the wrong speed limit status, with the potential to cause confusion for drivers or potential unsafe situations for workers. Issues with incorrect manual setting of the speed limit may be remediated with proximity (mobile on-person at location) sensors that would change the digital speed limit display automatically based on worker presence. Research is needed to determine the appropriate worker proximity sensor settings to activate/deactivate the 45 mph WWP display, understand DSLs impact on driver behavior and travel speed through the work zones under various conditions as compared to standard static 60/45 WWP signage. Also, additional research would help in determining the appropriate placement, spacing, and duration of placement of the DSLs for the highest rate of work zone speed limit compliance.

Language

• English

Project

• Status: Active
• Sponsor Organizations:

  Michigan Department of Transportation

  Van Wagoner Building
  425 W. Ottawa Street
  Lansing, MI  United States  48909
• Performing Organizations:

  Michigan State University, East Lansing

  Department of Civil & Environmental Engineering
  Institute for Community Development
  East Lansing, MI  United States  48824-1226
• Principal Investigators:

  Gates, Timothy

• Start Date: 20250505
• Expected Completion Date: 20270430
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Digital displays; Sensors; Speed limits; Traffic signs; Traffic speed; Work zone safety
• Geographic Terms: Michigan
• Subject Areas: Construction; Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 01957455
• Record Type: Research project
• Source Agency: Michigan Department of Transportation
• Files: RIP, STATEDOT
• Created Date: Jun 6 2025 2:32PM