Wisconsin Highway Delay Causation Study

Project summary

This study developed a reproducible framework for WisDOT to measure highway delay and examine its contributing factors. It integrated 15-minute travel times with traffic volumes, crash and incident records, lane closures, weather, and roadway information. The framework separates recurrent delay from delay above a historical baseline, matches excess delay to available event indicators, and retains unmatched delay as unclassified.

Across 2019, 2023, and 2024, non-recurrent delay represented approximately 73–75% of statewide delay. In 2024, total delay reached 32.6 million vehicle-hours, with 81% occurring within metropolitan planning areas. Work-zone-related delay accounted for approximately 24% of the statewide total. Analysis of 12 corridors revealed localized hotspots and substantial differences in delay patterns, including concentrations on signalized segments and upstream queue spillback.

The project delivered repeatable statewide and corridor reporting methods, supported by scripts and examples for future use. Changes in NPMRDS data supply and observation coverage warrant caution when comparing delay estimates across years, particularly 2023 and 2024.