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Figure ES.8. Inconsistency in performance measures for planning process. The L02 project provides a number of methods for analyzing travel time reliability and suggests that users present results in terms of CDF or semi-variance. Other SHRP 2 projects (e.g., L07, L08, and C11) provide tools for testing the reliability impacts of projects. While these tools summarize the reliability impacts in a variety of performance measures, the measures differ from the ones used to identify the travel time reliability problem in L02. L07 and C11 provide methods for estimating the value of the travel time reliability benefits, but they differ in the performance measures used to estimate the value of the benefits. FREEVAL-RL will need to adopt one of these two methods if it is to calculate the value of reliability benefits. When the SHRP 2 projects are examined together, they could benefit from standardization in the measures used to identify reliability problems, test solutions, and calculate user benefits. Suggested Research The stakeholders involved in the Southern California pilot site responded positively to the results produced by the product testing. It was suggested that the tools used could be applied across multiple freeways in the region to be able to identify causal factors of congestion as well as compare among different facilities. SHRP 2 implementation should involve further testing of the SHRP 2 products at the pilot sites and additional locations following revision of the tools in order to address the quick fixes suggested by the four current pilot sites. The Southern California pilot site found that the C11 tool produced reliability benefits in a narrow range between 29 percent and 36 percent of total benefits (from 30 percent to 32 percent for the I-5 facility and from 29 percent to 36 percent for the I-210 facility). Since this finding is based on a limited number of observations, more 14
testing is suggested to see if this finding holds true across different pilot sites and for different types of projects. Additional freeways could also test the various calibration methods proposed by the four pilot sites. Most of these calibration methods are a function of changing capacity. Further research could test whether similar capacity adjustments are warranted at other sites. The current SHRP 2 tools are unable to test many of the common operational strategies used in Southern California. The SHRP 2 program could collect a list of operational strategies from the four pilot sites and conduct research on the impacts of these types of projects on travel time reliability, following the approach adopted for L07. 15
