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 45.0 161 10633 1 0 0% 0 All 38.3 203 10633 0.85 0.6 11.8% 39 10.0 1.26 1.74 0.38 Before 31.2 243 10633 0.69 1.0 20.0% 68 7.8 1.51 1.83 0.22 After 45.4 164 10633 1.01 0.2 3.6% 9 6.1 1.02 1.35 0.33 Difference 14.1 -79 0 0.31 -0.8 -16.4% -59 -1.7 -0.49 -0.48 0.11 Difference% 45.2% -32.5% 0% 45.2% -81.8% -81.8% -86.2% -21.7% -32.5% -26.2% 52.2%