United States Department of Transportation
i
Performance Measures to Characterize Directional Corridor Travel Time Delay Based on Probe Vehicle Data : Final Report
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2015-10-01
[PDF-4.80 MB]
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Edition:Final report
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Abstract:Anonymous probe vehicle data are currently being collected on roadways throughout the United States. These data are being incorporated into local and statewide mobility reports to measure the performance of freeways and arterial systems. Predefined spatially located segments, known as Traffic Message Channels (TMCs), are spatially and temporally joined with probe vehicle speed data. Through the analysis of these data, transportation agencies have been developing agency wide travel time performance measures. One widely accepted performance measure is travel time reliability, which is calculated along a series of TMCs. Travel time reliability is usually measured as a percentile of base travel time or speed. When reliable travel times are not achieved because of incidents and recurring congestion, it is desirable to understand the time and location of these occurrences to proactively manage the corridor. This research emphasizes a visually intuitive methodology that aggregates a series of TMC segments based on a cursory review of congestion hot spots within a corridor. Instead of a fixed congestion speed threshold, each TMC link is assigned a congestion threshold based on the 70th percentile of the 15-minute average speeds between 2AM and 6AM. An analysis of approximately 90-million speed records collected in 2013 along I-80 in northern New Jersey was performed for this project. Travel Time Inflation, the time exceeding the expected travel time at 70% of measured free flow speed, was used to evaluate each of the 166 directional TMC segments along 70 miles of I-80. This performance measure accounts for speed variability caused by roadway geometry, heavy traffic flows, and other Highway Capacity Manual speed-reducing friction-factors associated with each TMC. A t-stat analysis based on unequal means was conducted to compare each of the TMC segments to determine statistical similarities of adjacent TMCs. An example analysis of 5 Million records in 2013 during the AM Peak eastbound direction of I-80 in northern New Jersey was performed for this research. The results determined that of the 83 segments in the eastbound direction there were 25 statistically similar groups.
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