New performance measures identify truck delays and bottlenecks

highway

Twin Cities businesses need a reliable and accessible freight network to compete in the Upper Midwest and beyond. However, many of the metro’s roadways are clogged with traffic during peak periods, disrupting truck schedules.

In a recent project, U of M researchers developed new performance measures to identify more clearly the extent of system impediments for freight vehicles during peak periods in select corridors. The study, sponsored by the Minnesota Department of Transportation (MnDOT), builds on previous research that identified area bottlenecks.

“In this and the previous study, we examined increasingly more detailed and specific data to learn just where and when congestion and delays develop within the roadway system,” says principal investigator Chen-Fu Liao, senior research associate in the Department of Mechanical Engineering. “Now, with knowledge of problematic locations and times of day, it will be possible to approach mitigation with a greater probability of success.”

For the study, the research team worked with stakeholders to prioritize a list of Twin Cities metro area (TCMA) freight corridors that have data coverage in the National Performance Measure Research Dataset (NPMRDS). (The dataset includes travel-time data from probe vehicles at five-minute intervals for all National Highway System facilities.)

Researchers obtained 24 months of NPMRDS data covering the selected corridors, along with GIS-based data and other travel-time sources. They then used their data analysis framework to generate measures of truck mobility, reliability, and delay at the corridor level. 

congested corridor chart
The top five congested AM and PM peak corridors in the Twin Cities
metropolitan area, with the average total daily delay for trucks
for those periods

“The precise tools and metrics revealed important information about truck mobility on different kinds of roadways, truck reliability on corridors during AM and PM peak periods, and the exact locations and extent of the delays within the TCMA highway system,” Liao says.

For example, truck congestion/delay measures revealed that the top five TCMA corridors with significant congestion had an average total delay on a regular weekday of more than 3,000 hours in the AM and PM peak periods, with the PM delays notably greater (see table above). Also, in the AM peak, eight additional interchanges had average daily delays of over 300 hours per mile. In the PM peak, nine interchanges and eight segments showed significant congestion.

All reliability measures indicated that truck travel time in the PM peak period is less reliable than in the AM peak period. Roadways with signalized or unsignalized intersections were less reliable for truck traffic than freeways. The truck mobility analysis found that roadways with intersections have higher travel times, particularly on county roads in the AM and PM peak periods.

“This research provided tools and metrics with levels of precision we didn’t have before concerning truck congestion,” says Andrew Andrusko, principal transportation planner with MnDOT’s Office of Freight and Commercial Vehicle Operations. “We needed the results of this research project to be able to take the next steps toward future investment in addressing freight bottlenecks and other strategic remedies.”

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Michael McCarthy
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