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Figure 6.8. Incident site and treatment inputs for L07 Analysis Tool. Limited Urban Area Operational Strategies While the L07 Analysis Tool provides a broad array of treatment options, the tool does not include several of the common operational strategies that can benefit urban facilities. The study team wanted to test several strategies not found in the tool: advanced ramp metering, auxiliary lanes, and ramp modifications. These are strategies commonly used by Caltrans and its partners in Southern California. As a result, the study team was required to estimate adjustments similar to those used for the C11 tool to estimate the benefits of these strategies. The L07 Analysis Tool would benefit from having a longer list of treatments that the user can test directly. The tool should be modified to include strategies tested at the four SHRP L38 pilot sites. 6.3 Baseline Condition Estimation of the L07 Analysis Tool As indicated previously, the team originally attempted to establish an estimation of baseline conditions by adjusting the FFS (see Figure 6.9). 110
Figure 6.9. Free-flow speed input for L07 Analysis Tool. Adjusting the FFS makes the tool select a different capacity for the facility according to the correspondence table shown in Table 6.1. This correspondence table is found in a part of the tool hidden from the user. A password is needed to view and modify the correspondence table. 111
Table 6.1. Free-Flow Speed/Capacity Correspondence Table Freeway Capacity 2010 HCM (pg. 11- 3&4) mi/h pc/h/ln 55 2250 60 2300 65 2350 70 2400 75 2400 As indicated earlier, the method of tricking the tool into utilizing a different capacity by adjusting the FFS was not effective, since the range of possible capacities is limited to those in the FFS-to-capacity correspondence table (Table 6.1). Following the discovery of the correspondence table, the study team was able to calibrate the tool by typing new capacities in the correspondence table. As seen in Figure 6.10, calibrating by FFS was somewhat successful (pink line), but calibrating the model by adjusting the capacity directly was even more effective (blue line). Figure 6.10. Mean TTI results for I-210 baseline condition estimation runs. Unlike the C11 toolâs calibration exercise, the L07 tool did not require an adjustment of the hourly distribution of demand, since this hourly distribution is already a required input. Also, unlike the C11 toolâs calibration exercise, the L07 toolâs calibration effort could be accomplished with a more realistic capacity of 2,690 vphpl (the C11 tool was calibrated to 1,300 vphpl) for the I-210 facility. However, neither capacity corresponds to the maximum throughput measured in PeMS for the facility. This discrepancy stems from the definition of capacity in the Highway 0.00 0.50 1.00 1.50 2.00 2.50 3.00 2,400 vphpl (70 mph FFS) 2,690 vphpl (direct entry) PeMS 112
