Travel Time Reliability Reference Manual/Example Data

Below are graphs and data for an 6-lane urban freeway (I-43/I-894 near Milwaukee) and 4-lane inter-regional (I-94 west of Eau Claire). All data comes from the NPMRDS data set in January 2012.

6-lane urban freeway (4.35 miles) Free flow travel time is based on the 70th percentile travel time

Reliability Index Value
TTI 1.01
BI 0.26
OPT 94.90
PTI 1.27
TTI80 1.02
MI 1.40


Travel Time in minutes
Mean 4.58
Free Flow 4.55
95th % 5.76
80th % 4.65
97.5th % 6.47


4-lane interregional freeway (20.18 miles) Free flow travel time is based on speed limit of 65mph

Reliability Index Value
TTI 1.03
BI 0.06
OPT 98.40
PTI 1.09
TTI80 1.038
MI 1.150


Travel Time in minutes
Mean 19.26
Free Flow 18.63
95th % 20.38
80th % 19.33
97.5th % 21.42

The 3-D graphs below show travel times by day and by hour for each corridor. Visually, one can see the better reliability of the inter-regional corridor over the urban. Blank areas represent points where real-time data did not exist along the entire corridor.

Travel Times for 6-lane Urban Freeway in January 2012

Travel Times for 6-lane Urban Freeway in January

Travel Times for 4-lane Inter-regional Freeway in January 2012

Travel Times for 4-lane Inter-regional Freeway in January

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Travel Time Reliability Reference Manual