Consider Automating Weather-Related Messages on Digital Message Sign Systems, in Addition to Travel Times, Using Data from Environmental Sensor Stations.

State Study Provided Recommendations for Automation and Readability of the Messages Used in the Dynamic Message Sign System in Michigan.

Date Posted
08/31/2023
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Identifier
2023-L01190

Quantifying Effectiveness and Impacts of Digital Message Signs on Traffic Flow

Summary Information

Digital Message Signs (DMS) (also referred to as dynamic message signs, variable message signs, or changeable message signs) are an important part of the Advanced Traveler Information Systems (ATIS) that display a variety of real-time travel information for the road users, including traffic diversion, travel time, congestion, upcoming roadwork, lane closures, and incidents such as traffic accidents. Other information includes inclement weather, speed regulations, special events, and safety related messages such as seatbelt usage. Given limited budgets and time constraints, it is important for DOTs to be aware of the most efficient DMS practices. Therefore, this study evaluated different DMS message types and installation locations in Grand Rapids, Saugatuck, and Saginaw, Michigan by developing a data-driven methodology involving field case studies, Virtual Reality (VR) simulation, and user surveys, utilizing a variety of data collected from 2019 to 2021. The study also generated results to facilitate better allocation of Michigan DOT’s (MDOT) resources by investing in effective sign technologies for traffic improvement and improve overall DMS operational practices.

Lessons Learned

  • Consider automating weather-related messages, in addition to travel times. This study clearly demonstrated that it is possible to automate the display of weather-related messages using Environmental Sensor Stations (ESS) detections. The researchers also found that automation priority should be given to the time-sensitive messages that require immediate actions to be taken by drivers based on the detected conditions, for example “ROAD MAY BE SLIPPERY, REDUCE SPEED”. However, additional research is needed to address practical issues such as ESS location relative to DMS and automation decision thresholds. 
  • Get the message across clearly. When conveying the location of an event to drivers using DMS messages, street names should be indicated more clearly to avoid confusing drivers who may be unfamiliar with the area. The survey results showed that almost half of the respondents stated that a message such as “CONGESTION AFTER MARKET” was unclear compared to a message such as “CONGESTION AFTER MARKET AVE”.
  • Time the phasing of long DMS messages appropriately to enable readability by drivers. The survey participants stated having difficulties reading messages when operated in phases. Also, the VR simulation study confirmed the existence of potential issues associated with phasing time and message length. The researchers recommend a shorter phasing time (2.5 seconds) rather than longer phasing alternatives of four seconds, to facilitate drivers’ ability to read the DMS messages more easily, still suggesting further research be conducted on the issue.
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