Reliability Performance Measure Methodology
Reliability categories are determined by comparing the Buffer Time Index and average speed. I-15 is segmented into 1-mile segments between Payson and Brigham City as well as in Southern Utah during the PM Peak Hour.
The Reliability Score is determined by the percentage of Reliably Fast 1-mile segments. Reliably Slow and Unreliable segments get a score of 0. The freeway segment values are weighted by their VMT.