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Intelligent Transportation Systems & Signals

Underbridge inspection units (UBIUs) that reach from above deck to below.
Department of Transportation

Intelligent Transportation Systems & Signals

Effective Bridge Deck Weather Warning Technologies

Project Number: SPR-1728

Contract Number: 2021-0412

Status: Complete

Start Date: 02/15/2021

End Date: 12/22/2024


Warning signs are typically deployed at bridges to warn motorists of potential icy surface conditions on the bridge, although the effectiveness of these signs is questionable. One potential improvement is the bridge deck warning system (BDWS), which activates a flashing warning sign border or beacon based on real-time weather and bridge surface data. However, such systems have not been broadly implemented, and consequently, their effectiveness as a safety countermeasure is not well established. To address this knowledge gap, research was performed to evaluate BDWS strategies in terms of their impacts on driver behavior and safety performance during winter driving conditions, and to provide guidance to support future deployments of BDWS within Michigan. A series of winter field evaluations were performed along three freeway bridges in Michigan to assess the effectiveness of various BDWS strategies as a speed reduction countermeasure for motorists approaching a potentially icy bridge. The results showed that a BDWS with a flashing LED border reduced motorist speeds when encountering a bridge during winter weather conditions compared to the standard MUTCD W8-13 warning sign, and this effect was consistent between passenger cars and heavy trucks. Greater speed reductions were observed when the BDWS sign was combined with a dynamic speed feedback (DSFS) sign that displayed a “SLOW DOWN” or “ICY ROAD” message to approaching motorists, with the strongest effects observed when the message was pulsed at 1 hertz. Speed reductions were also observed when a “SLIPPERY ROAD CONDITIONS / REDUCE SPEEDS” message was displayed on a full-size DMS located at the subject bridge. A preliminary analysis of crashes before and after installation of the current BDWS implementations in Michigan found that winter-season target crash frequencies were lower at 16 of the 20 sites after installation of the BDWS. Collectively, the findings of this research suggest that BDWS help improve driver behavior and safety performance at bridges during winter driving conditions in Michigan, and continued implementation and operation of BDWS is recommended. The research findings were utilized to develop guidelines and recommendations towards future implementation and operation of BDWS in Michigan, including selection of sites, sign types, warning alerts and messages, sensors and related equipment.




Research Manager Project Manager Performing Organization
Andre Clover Dave Smith Michigan State University