Updating And Implementing The Grade Severity Rating System Gsrs For Wyoming Mountain Passes

Updating and Implementing the Grade Severity Rating System (GSRS) for Wyoming Mountain Passes

Updating and Implementing the Grade Severity Rating System (GSRS) for Wyoming Mountain Passes

The state of Wyoming like other western states is characterized by steep downgrades on mountainous highways. These downgrades present considerable crash risks to drivers of trucks and other heavy vehicles inexperienced or unfamiliar with the challenging terrain. This has resulted in crashes that have had devastating consequences on lives and property. A major contributory factor to truck crashes on mountain passes has been brake failure due to heating. The risk of truck brake failure on downgrades is high due to the large amounts of heat energy that have to be absorbed by the brake system. The Grade Severity Rating System (GSRS) was developed in the early 1980s to enhance truck safety on downgrades by recommending maximum safe descent speeds through Weight Specific Speed (WSS) signs. However, truck designs, brake and engine characteristics have changed during the intervening decades since the development of the GSRS. This has warranted updating the GSRS to reflect current truck characteristics. The GSRS model parameters were updated using field testing as part of this research. Validation tests conducted indicated the updated GSRS can recommend descent speeds that reduce the risk of brake failure. The second part of the research related to evaluating the safety effectiveness of downgrade warning signs as well as identifying factors impacting truck crash frequency/severity on mountain passes. The analysis showed that downgrade warning signs installed on mountain passes in the state are effective. A survey of intelligent transportation system (ITS) technologies identified applications that may be adopted to improve warning sign effectiveness. The results of the analyses also indicated that different factors including driver, vehicle, downgrade, and traffic characteristics influence crash frequency and severity on mountain passes. Suitable countermeasures were proposed to reduce crash frequency/severity. Implementation of the findings and recommendations from this research will engender driver compliance and confidence in the new advisory speeds, thereby improving mountain pass safety. Stakeholders that may benefit from this study include the Wyoming Highway patrol, Wyoming Department of Transportation (WYDOT), trucking companies and the general public.

Updating and Implementing the Grade Severity Rating System (GRRS) for Wyoming Mountian Passes

"This study was instituted to update the GSRS model to recommend maximum safe descent speeds which that will reduce the incidence of downgrade truck crashes attributed to brake failure on Wyoming mountain passes." -- page 2.