Common use of Transit Travel Time Clause in Contracts

Transit Travel Time. Transit travel time data were calculated by using GPS position data. Table 9-3 shows the travel time statistics for the SR 99 corridor during the Phase Two test. The average transit travel time of eligible trips when TSP was on was 13 to 32 seconds shorter than that when TSP was off. With northbound and southbound together, the TSP saved an average of 26 seconds of transit travel time per trip, about 2.47 percent of the total corridor travel time. The mean transit travel time for the granted trips was even longer than that for all eligible trips with TSP off. This seems contradictory. However, given that only late trips would be granted TSP treatment, this result is not beyond our expectation. Another comparison between late trips with TSP on and off was conducted. The results showed that TSP saved 54 seconds of transit travel time (northbound and southbound together) for late trips, about 4.93 percent of the total corridor travel time. Table 9-3 Transit Corridor Travel Time in the Phase Two Test Eligible Trips with TSP Off Eligible Trips with TSP On TSP Granted Trips Standard Deviation Northbound 2′08″ 3′12″ 3′12″ Southbound 2′34″ 2′20″ 2′20″ Maximum Northbound 22′47″ 25′13″ 25′13″ Southbound 24′23″ 24′16″ 24′16″ Minimum Northbound 12′13″ 9′43″ 9′43″ Table 9-4 shows the transit travel times across the three biggest intersections on this corridor. The starting and ending points for intersection travel time calculation were defined as the points 100 ft upstream and 100 ft downstream of the intersection’s center point, respectively. Note that this definition is different from the one used for the Phase One test. The decision to use 100 ft upstream and downstream of the intersection’s center point was intended to exclude all bus stops from the intersection travel time calculation. This was not possible for the Phase One test because several near-side bus stops were too close to the intersections. All the bus stops in the Phase Two test corridor were on the far side and over 200 ft away from the center of the intersection. Southbound 40 28 200th Street Northbound 33 20 Southbound 34 31 220th Street Northbound 37 34 Southbound 23 26 Standard Deviation (sec) 196th Street Northbound 37 36 Southbound 27 23 200th Street Northbound 25 14 Southbound 24 19 220th Street Northbound 29 20 Southbound 22 26 As can be seen in Table 9-4, the SS-RTSP system saved transit travel times at all studied intersections except for the southbound direction of the 200th St intersection. The time savings varied from 0 to 12 seconds, or 30 percent of the travel time without TSP. The reason for the travel time increase in the southbound direction of the 200th St intersection is unknown, but it is very likely due to random variations of traffic conditions between the two test weeks or bad TSP and traffic signal timing combinations, as will be discussed in Chapter 10.