Vehicle Delays and Stops. Average delay per vehicle is the MOE used for intersection level of service evaluation in the HCM (Transportation Research Board 2000). In this study, we used averaged vehicle delay and number of vehicle stops to reflect the time loss of vehicles at intersections. Changes in this MOE set before and after implementation of the SS-RTSP system would indicate the impacts of the TSP system on intersection performance. Additionally, it could also be used to quantify the impacts of the SS-RTSP system on side streets crossing the TSP corridors.
Vehicle Delays and Stops. The control delay per vehicle is the only measurement representing the level of service (LOS) at signalized intersections (Transportation Research Board 2000). Vehicle delays at major cross streets were manually collected from traffic video images. Table 8- 6 shows the average vehicle delays calculated from the manually collected vehicle delay data for April 4 and 11, 2006. We used a paired t-test to compare the cross-street vehicle delays before and after the SS-RTSP implementation. The t ratio was 1.799, which was smaller than the critical t ratio of 1.962 at p=0.05 level. Therefore, the change of control delay for vehicles on side streets was not significant at p=0.05 level after the SS-RTSP implementation. Table 8-6 Vehicle Delays in the Phase One Test Intersection Time Period Approach Intersection Delay (Second) TSP Off Alderwood 7:30am - 8:00am North approach 25.09 Alderwood 2:00pm - 2:30pm North approach 41.84 Alderwood 4:30pm - 5:00pm North approach 42.50 Alderwood 7:30am - 8:00am South approach 26.47 Alderwood 2:00pm - 2:30pm South approach 37.30 Alderwood 4:30pm - 5:00pm South approach 35.94 36th Ave. 7:30am - 8:00am West approach 17.72 36th Ave. 2:00pm - 2:30pm West approach 18.12 36th Ave. 4:30pm - 5:00pm West approach 25.03 TSP On Alderwood 7:30am - 8:00am North approach 30.22 Alderwood 2:00pm - 2:30pm North approach 27.76 Alderwood 4:30pm - 5:00pm North approach 42.64 Alderwood 7:30am - 8:00am South approach 25.54 Alderwood 2:00pm - 2:30pm South approach 20.77 Alderwood 4:30pm - 5:00pm South approach 31.96 36th Ave. 7:30am - 8:00am West approach 11.83 36th Ave. 2:00pm - 2:30pm West approach 17.55 36th Ave. 4:30pm - 5:00pm West approach 23.96 The intersection control delays and number of vehicle stops for all approaches were also collected from the simulation experiments. Table 8-7 shows the average control delay and number of stops at each intersection. For three of the four intersections, the SS- RTSP system decreased average intersection control delay and number of stops. The only exception was the intersection of NorthPoint, where both average control delay and number of stops increased slightly after the SS-RTSP implementation. Because this intersection was less busy than the other three, the negative impacts from the SS-RTSP system were probably not enough to offset the positive impacts at other intersections. However, paired t-tests on average control delays per vehicle and numbers of vehicle stops did not indicate significant impacts f...
Vehicle Delays and Stops. Control delays and vehicle stops were collected for all approaches from the simulation experiments. Table 9-6 shows the average control delay and number of stops at each intersection in one simulation iteration. Table 9-6 Traffic Delays and Stops from One Simulation Iteration in the Phase Two Test TSP on TSP off Intersections AVD1 ANS2 VC3 AVD ANS VC 164th ST. 13 0.54 7332 13 0.55 7325 168th ST. 29.3 0.74 9494 29 0.75 9499 174th ST. 10.8 0.4 8516 10.7 0.42 8515 176th ST. 15.4 0.57 9730 15.3 0.56 9730 188th ST. 36.3 1.21 9820 35.8 1.23 9832 196th ST. 36.2 1.01 12324 36.6 1.03 12307 200th ST. 37.4 1.08 10441 38.4 1.03 10446 208th ST. 26.2 0.79 10656 25.9 0.79 10647 212th ST. 18.9 0.81 10876 18.9 0.78 10871 216th ST. 16.9 0.74 10267 16.9 0.72 10265 220th ST. 39.1 1.01 12226 38.5 1.05 12235 224th ST. 9.4 0.35 9806 9.1 0.39 9789 238th ST. 13.8 0.48 9677 13.5 0.5 9673 Total 24.1 0.77 131134 24.2 0.77 131165 1 denotes average vehicle delay; 2 denotes average number of stops; 3 denotes vehicle count Given that each simulation run was just a random sampling action from a stochastic process, no conclusion can be drawn from a single simulation iteration. To further examine the differences in vehicle delay and number of stops between the conditions of TSP on and TSP off, ten simulation iterations were conducted. Each was associated with a unique random seed. Vehicle delays and stops were averaged for all 13 intersections under each test scenario. Table 9-7 presents the comparison results for all ten simulation iterations. Table 9-7 Traffic Delays and Stops from All Simulation Iterations in the Phase Two Test AVD1 ANS2 VC3 Simulation Iteration TSP On TSP Off TSP On TSP Off TSP On TSP Off 2 24.2 24.3 0.78 0.78 131877 131882 3 24.0 24.1 0.77 0.78 131307 131308 4 23.9 23.7 0.77 0.76 130552 130557 5 24.6 24.4 0.82 0.79 130872 130831 6 24.5 24.5 0.81 0.80 132680 132699 7 24.1 24.2 0.78 0.79 131429 131459 8 24.1 24.1 0.77 0.78 132060 132087 9 24.0 23.8 0.76 0.75 130936 130934 10 23.9 23.8 0.78 0.77 131839 131844 Total 24.2 24.1 0.78 0.78 131472 131474 Paired t-test at the p=0.05 level Not significant Not significant Not applicable 1 denotes average vehicle delay; 2 denotes average number of stops; 3 denotes vehicle count The average vehicle delays and the number of stops observed from the ten simulation iterations varied slightly from iteration to iteration. TSP impacts on average vehicle delays were contradictory: for some iterations, vehicle delay increased, while for othe...
