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Figure 5.22. Comparison of mean TTI and percent reduction on I-5 for high-occupancy Vehicle + GP widening test. 5.5 Results of the I-210 Scenario Testing The second facility tested was the 16-mile congested urban segment of I-210 in Los Angeles County (see Figure 5.23). This facility has four to five mixed-flow lanes in each direction, as well as barrier-separated high-occupancy vehicle and auxiliary lanes. Congestion exists on the facility 6 hours per day per direction. This congestion is heavily directional due to the location of major job centers toward the west and primarily residential communities toward the east. All scenarios on the I-210 facility were tested in the eastbound direction. As a result, they reflect congestion mainly in the p.m. peak period when travelers are returning home from work. 91
Figure 5.23. Map of I-210 facility in Los Angeles County. Split Segment Test Following the initial run of the entire 16-mile facility, the team split the facility into smaller segments to determine whether the tool would produce more accurate results with smaller segments. Since the tool requires the user to input a single Number of Lanes value for each test, the facility was split into two segments based on the number of lanes in each segment (Figure 5.24). 92
Figure 5.24. I-210 eastbound segmentation. The reliability results of the full 16-mile segment of the urbanized area of I-210 are shown in Figure 5.25 (same chart as Figure 5.7 from âBaseline Condition Estimationâ section). Figure 5.25. Mean TTI on the I-210 for full 16-mile segment. For each of the two smaller segments, the study team conducted the same exercise as in the baseline condition estimation. The actual hourly distribution of traffic volumes was entered into the tool as the hourly variation in demand, and the results were calibrated to the actual baseline conditions reported in PeMS by adjusting peak capacity. Figures 5.26 and 5.27 show the results of these tests. As can be seen in the figures, the calibration seems to improve slightly from the full 16-mile facility to the five-lane segment. However, the calibration for the 4-mile segment does not improve significantly. In both cases, the segmentation is unable to correct the key inaccuracies of the slight hump in TTI in the a.m. peak period and horizontal shift in TTI in the p.m. peak. 93
Interestingly, the reliability estimates from the C11 tool for the four-lane segment and the five-lane segment are more similar to each other than to the baseline conditions. These results suggest that breaking up the facility into similar segments does not significantly improve the calibration, and even finer segmentation is probably not worth the effort when modeling the reliability impact of projects in the C11 tool. Figure 5.26. Mean TTI on the I-210 for 5.3-mile five-lane segment. Figure 5.27. Mean TTI on the I-210 for 10.2-mile four-lane segment. As seen later in Section 6.5, the same I-210 segmentation was tested using the L07 tool. In that tool, the four-lane segment was able to be calibrated far more closely to PeMS conditions than the five-lane segment. Given that the C11 tool produces relatively similar reliability results 94
for the four-lane and five-lane segments, the study team decided to perform all future tests utilizing only the four-lane segment to allow for comparability between the tools. Incident Duration Tests The study team utilized the C11 Reliability Analysis Tool to test the effects of a reduction in incident duration that had been tested in the Caltrans I-210 CSMP. In that CSMP scenario, a collision duration of 50 minutes was reduced to 38 minutes. As seen in Figure 5.28, the C11 Reliability Analysis Tool allows for the input of a percent reduction in incident duration. Therefore, a percent reduction of 24 percent (the reduction from 50 to 38 minutes) was used for this test. Figure 5.28. Incident management strategy input. As shown in Figure 5.29, the results exhibit a noticeable improvement in reliability as a result of the incident reduction. Figure 5.30 shows the percent reduction in TTI was generally greater when the original TTI value was greater. This does not appear to be universally true, however; although the original TTI at 3:00 p.m. was higher than the original TTI at 4:00 p.m., the 3:00 p.m. TTI saw a smaller percent reduction than the 4:00 p.m. TTI. 95
Figure 5.29. Mean TTI on the I-210 for incident duration test. Figure 5.30. Comparison of mean TTI and percent reduction on the I-210 for incident duration test. 96
Peak Capacity Tests The study team also tested several additional scenarios identified in the I-210 CSMP (SCAG and Caltrans 2010) using the C11 toolâs Peak Capacity input feature (see Figure 5.31). To estimate the improvement in the capacity for each scenario, the study team estimated the increase in total VMT in the corresponding microsimulation runs from the CSMP. The results of these tests are shown in Figures 5.32 through 5.36. The capacity adjustments were used later when the entire facility was reanalyzed for the benefit-cost analysis. This analysis is described in Chapter 8. Figure 5.31. Peak capacity input. 97
Figure 5.32. Mean TTI on the I-210 for ramp metering test (Scenarios 1 and 2). Figure 5.33. Mean TTI on the I-210 for advanced ramp metering test (Scenarios 3 and 4). 98
Figure 5.34. Mean TTI on the I-210 for auxiliary lane test (Scenarios 5 and 6). Figure 5.35. Mean TTI on the I-210 for ramp closure test (Scenarios 7 and 8). Figure 5.36. Mean TTI on the I-210 for on-ramp and auxiliary lane test (Scenarios 9 and 10). 99
