Signal Cycle Failure. Signal cycle failure (or overflow) is an interrupted traffic condition in which a number of queued vehicles are unable to depart because of insufficient capacity during a signal cycle. From a motorist’s point of view, cycle failure can be more easily perceived than average control delay or queue length. Signal cycle failure data were also manually collected from traffic video images. Table 8-9 shows the frequency of signal cycle failure at cross-streets on the Mondays of the two study weeks. Table 8-9 Signal Cycle Failure Occurred in the Phase One Test Intersection Cross-Street Signal Cycle Failure per Cycle Standard Deviation Maximum Number of Vehicles in a Failure TSP Off Alderwood Mall Parkway South approach 0.01121 0.12492 2 Alderwood Mall Parkway North approach 0.00229 0.04789 1 36Ave West approach 0.00000 0.00000 0 TSP On Alderwood Mall Parkway South approach 0.00909 0.19069 4 Alderwood Mall Parkway North approach 0.00000 0.00000 0 36Ave West approach 0.00413 0.11134 3 Again, we used the paired t-test to compare the average frequency of signal cycle failures before and after the TSP implementation. The t ratio was 0.044, which was much smaller than the critical value of 2.920 at p=0.05. Therefore, the change in the average number of signal cycle failures after the TSP implementation was not significant at the p=0.05 level. The frequency of signal cycle failures may have slightly increased or decreased, depending on flow and signal control conditions after TSP was enabled. When TSP was on, the standard deviation of signal cycle failures may also have increased or decreased in a narrow range. The maximum number of vehicles caught in one cycle failure may also have increased or decreased after TSP was turned on. This was consistent with the cross-street queue length analysis described in Section 8.3.2.
Signal Cycle Failure. Signal cycle failure (or overflow) is an interrupted traffic condition in which a number of queued vehicles are unable to depart because of insufficient capacity during a signal cycle. From a motorist’s point of view, cycle failure can be more easily perceived than average control delay or queue length. Signal cycle failure data were also manually collected from traffic video images. Table 9-9 shows the frequency of signal cycle failure at cross-streets. We also applied a paired t-test to compare the average frequency of signal cycle failures before and after the TSP implementation. The t ratio was 0.450, which was much smaller than the critical value of 1.962 at p=0.05. Therefore, TSP implementation did not result in significant changes in the average number of signal cycle failures. The frequency of signal cycle failures may have slightly increased or decreased, depending on flow and signal control conditions after TSP was turned on. When TSP was on, the standard deviation, maximum, and median of signal cycle failure occurrence may have increased or decreased in a narrow range. This is consistent with the cross-street queue length analysis described in Section 9.3.2. Table 9-9 Signal Cycle Failure in the Phase Two Test Intersection Approach Signal Cycle Failure Per Cycle Standard Deviation Maximum TSP Off 164th Street Westbound 0.0077 0.0877 1 164th Street Eastbound 0.0294 0.2706 3 174th Street Westbound – through 0 0 0 174th Street Westbound – Left turn 0.0588 0.2388 1 174th Street Eastbound– through 0 0 0 174th Street Eastbound– Left turn 0.5000 1.2702 7 TSP On 164th Street Westbound 0.0643 0.3640 3 164th Street Eastbound 0.0286 0.2667 3 174th Street Westbound– through 0 0 0 174th Street Westbound– Left turn 0.0260 0.2279 2 174th Street Eastbound– through 0 0 0 174th Street Eastbound– Left turn 0.5865 1.3034 8 CHAPTER 10 SIMULATION-BASED INVESTIGATION OF TSP SYSTEM OPERATION AND OPTIMIZATION TSP systems have been implemented in many urban areas in the U.S. and are regarded as one of the most applicable countermeasures against traffic congestion, particularly for metropolitan areas. Most of the relevant research has concentrated on system performance evaluations, with few studies emphasizing TSP operation strategies or system control optimization. This report lays out a series of theoretical and practical issues regarding TSP system control on the basis of observed field data and comprehensive analysis. Further research is desirable to improve the curr...
