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Figure ES.4. Calibration of C11 tool on the I-210 by comparing mean Travel Time Index (TTI). Benefit-Cost Findings After exploring the calibration and modeling capabilities of the three SHRP 2 analysis tools, the study team examined the impact of adding travel time reliability to benefit-cost analysis. The team found that the C11 tool was relatively easy to use and provided reasonable results, so this tool was used to estimate the reliability benefits of projects. Figures ES.5 and ES.6 show how the CSMP benefit-cost analysis changed with the inclusion of travel time reliability benefits. The shaded portion of the bars indicates benefits due to improvements in travel time reliability, while the solid portion indicates the benefits in the original benefit-cost analysis found in the CSMP. While the ramp metering scenario resulted in a very high benefit-cost ratio, the C11 tool does not seem to show a large benefit from improving travel time reliability on the facility. However, operational improvement benefits are reflected in the total benefits calculated, which include travel time savings, vehicle operational cost savings, and emission cost savings. The addition of reliability benefits did not affect the rank order of projects on either facility in terms of total user benefits or benefit-cost ratios. Nevertheless, it may make a marginal project cost beneficial (benefit-cost ratio above one). Furthermore, travel time reliability can make a difference in the ranking of projects that have very similar benefits. 8
Figure ES.5. Benefit-cost results for I-5 facility with C11 reliability estimate modified. Figure ES.6. Benefit-cost results for I-210 facility with C11 reliability estimate modified. Original Benefits from CSMP Modified Reliability Benefits Scenario Project Cost Original Benefits from CSMP Modified Reliability Benefits Scenario Project Cost 9
