FHWA Freight Movement and Economic Vitality Metrics

Truck Travel Time Reliability

Truck travel time reliability (TTTR) is reported to FHWA for interstates.  This metric is determined for each segment by calculating the ratio of the 95% percentile drive time divided by the 50th percentile drive time multiplied by the total segment miles.  TTTR values are summed for all segments and divided by total length. Five time periods are used in the assessment (including holidays) with the maximum TTTR value used in the calculation. Assessed time periods include: 
  • Weekday 6-10am; 10am-4pm; 4-8 pm
  • Weekends 6am -8pm
  • Overnight for all days 8pm -6am
There is no target to determine reliability - instead
TTTR uses an overall performance index. More information regarding methodology is available by the FHWA