Use of Probe Speed Data to Assess Winter Maintenance Effectiveness

Date and Time: Tuesday, May 9, 2023: 10:00 AM - 12:00 PM
Location: Keck 100

 

Lead Presenter:  Dave Huft, Intelligent Transportation Systems Program Manager
Affiliation:  SD Department of Transportation
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Lead Presenter Biography

Dave Huft is the Intelligent Transportation Systems Program Manager at the South Dakota Department of Transportaton. For many years he directed SDDOT's Research Program, which conducted numerous studies related to road weather. He manages the Transportation Pooled Fund Study "Development of a Maintenance Decision Support System". He is active in the AASHTO Committee on Transportation System Operations.  

Co-Authors

Thad Bauer, Research Program Manager, SDDOT; Evan Haugh, Vanasse Hangen Brustlin Inc.

Presentation Description 

Winter maintenance is one of the SDDOT's most important and time-sensitive functions. SDDOT has measured winter maintenance performance by tracking inputs like labor or material use, which quantify the effort expended, but not results achieved. While other states had explored performance measures using traffic speed as a surrogate for road condition, but SDDOT had not.

During the 2020 – 2021 winter, SDDOT used Iteris ClearGuide data to: evaluate the quality and availability of probe data in SD; relate speed to winter road condition; assess probe data’s ability to detect deteriorating road conditions; assess probe data’s ability to detect winter crashes.

SDDOT observed differences of 2 to 10 mph between speeds from probe vehicles and calibrated automatic traffic recorders. Data availability was better during daytime working hours than nighttime hours, during weekdays than weekends, and in urban areas than in rural. Availability on Interstate highways ranged between 75 and 100 percent but fell below 35 percent on highways with less than 2500 ADT even during daytime hours.

Logistic regression defined a relationship between traffic speed and “clear” or “snow” road conditions based on camera images of pavement surfaces. Traffic speeds of 0 – 76 percent of free flow speed associated with snowy conditions, while speeds greater than 87 percent associated with clear conditions.

About one-third of reported crashes generated rapid drops and subsequent recovery of traffic speed, but the rest did not.

Based on this work, SDDOT will continue to pilot speed-based winter performance measures on roads with ADT > 2500.

Extended Summary

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