Analyzing and Predicting Truck Travel Time Reliability

About the report

Truck travel time reliability (TTTR) is one of the most important performance measures for assessing freight movement on the interstates. The Virginia Department of Transportation (VDOT) and the Virginia Office of Intermodal Planning and Investment have been reporting TTTR and setting performance targets as required by the Federal Highway Administration, as well as using TTTR in various project planning and performance measurement processes. This study aims to identify the locations and potential influencing factors of unreliable truck travel time, evaluate the effect of influencing factors, and develop models to predict the TTTR index for interstate highways in Virginia.

Using 7 years of probe speed and travel time data from the National Performance Management Research Data Set together with traffic volume, roadway, incident, and weather data maintained by VDOT, this study conducted descriptive and regression analyses to characterize the trends of TTTR and developed a hierarchical Bayesian model and random forest models to analyze and predict TTTR.

Hierarchical Bayesian models and random forest models achieved similar prediction performance, but the Bayesian model provides credible intervals for segment-level and network-level predictions to help VDOT planners better account for uncertainty in performance target setting and project planning. Traffic volume, crash frequency, the number of through lanes, and posted speed limit are the most significant factors in the Bayesian models and random forest models.

The study recommends that VDOT use the hierarchical Bayesian model to supplement the current method for setting freight reliability targets. Researchers developed an implementation plan that includes stakeholder engagement and technical assistance for the 2026–2029 performance cycle.

_{Disclaimer Statement:The contents of this report reflect the views of the author(s), who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Virginia Department of Transportation, the Commonwealth Transportation Board, or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. Any inclusion of manufacturer names, trade names, or trademarks is for identification purposes only and is not to be considered an endorsement.}

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