Freight Travel Time Reliability: Planning Time Index

Truck travel times vary greatly from day to day, and drivers remember those few bad days they suffered through unexpected delays. Travel time reliability measures the extent of this unexpected delay. Planning time index represents the additional time that a shipper should budget to ensure on-time arrival 95% of the time. Different from on-time arrival, the higher the planning time index (PTI), the worse the reliability is.

From 2018 and 2019, combination truck PTI during peak hour increased statewide from 1.55 to 1.56. For a trip that would take 10 minutes in free-flow conditions, the 95th percentile travel time is 15.6 minutes with a PTI of 1.56. The shipper needs to plan an additional 5.6 minutes for the trip to arrive on time.

Methodology

Methodology: Freight Travel Time Reliability: Planning Time Index

Combination truck travel times vary greatly from day to day, and drivers remember those few bad days they suffered through unexpected delays. Travel time reliability measures the extent of this unexpected delay. Planning time index (PTI) represents the additional time that a shipper should budget to ensure on-time arrival 95% of the time. Different from on-time arrival, the higher the PTI, the worse the reliability is.

From 2017 to 2018, combination truck PTI during peak hour/peak period increased statewide from 1.39 to 1.55. For a trip that would take 10 minutes in free-flow conditions, the 95th percentile travel time is 15.5 minutes with a PTI of 1.55. The truck driver needs to plan an additional 5.5 minutes for the trip in order to arrive on time.

Calculation

`"Travel Time"_("95th percentile")/"Travel Time"_("free flow")`

Reporting Periods

  • Peak Hour
  • Peak Period
  • Daily
  • Yearly

Sources

FDOT - Traffic Characteristics Inventory
HERE Technologies - Travel Time Data