Period Speed (mph) Travel Time (s) Distance (ft) Speed Ratio # of Stops Stop% Stop Time (s) Speed Variance (Standard Deviation) Travel Time Index (TTI)The Travel Time Index is the ratio of the peak-period travel time to the free-flow travel time. Planning Time Index (PI)The planning time index represents how much total time a traveler should allow to ensure on-time arrival. It is the ratio of the peak-period travel time to the free-flow travel time. Buffer Index (BI)The buffer index represents the extra time (or time cushion) that travelers must add to their average travel time when planning trips to ensure on-time arrival. Speed Limit 45.0 106 6977 1 0 0% 0 All 38.1 130 6977 0.85 0.4 6.9% 10 7.0 1.23 1.91 0.55 Before 25.7 188 6977 0.57 1.3 22.2% 40 3.9 1.78 1.93 0.08 After 40.7 118 6977 0.90 0.2 3.6% 3 3.8 1.11 1.29 0.16 Difference 15.1 -70 0 0.33 -1.1 -18.7% -37 -0.1 -0.66 -0.64 0.07 Difference% 58.7% -37.3% 0% 58.7% -83.9% -83.9% -92.1% -2.2% -37.3% -33.2% 84.5%