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⢠The C11 tool estimates benefits for the current year and a future year, but it does not estimate life-cycle benefits over a given time period. These can be approximated by interpolating and discounting the current and future year benefits outside the model. However, the life-cycle benefits can be estimated more accurately inside the model, if benefits are calculated for each year, summed, and discounted. The study team found that the recurring delay benefits did not match the benefits in the microsimulation models, which raises the question of whether the reliability benefits should be adjusted when detailed mobility modeling data are available. ⢠The L07 tool estimates life-cycle benefits by estimating benefits for the current year and assuming these benefits are constant over the life cycle. The tool needs to be modified to accommodate demand growth. The study team identified a workaround, but this involves multiple model runs and external calculations. ⢠The FREEVAL-RL tool does not estimate monetized user benefits using the reliability results. However, these could be calculated from the travel time reliability performance measures (i.e., standard deviation or 50th and 80th percentile TTI) and VMT data outputted by the model. The C11 and L07 tools use slightly different methods for calculating the value of the reliability benefits. One of these methods could be adopted for FREEVAL-RL. 9.2 Decision Maker Perceptions This section describes decision maker impressions on whether the analyses were easily understood and the results credible. These impressions are based on input from SCAG and Caltrans representatives as well as other stakeholders present at outreach meetings. How did policy makers react to the results? SCAG and Caltrans representatives agreed that considering reliability in the decision- making process would be an important step forward. The general findings from the product testing were understood by representatives, and participants particularly liked the L02 procedures to identify contributing factors. Some stakeholders suggested that the L02 approach could be applied to other freeways in Southern California. Other stakeholders were appreciative of SCAGâs involvement in the SHRP 2 testing and encouraged the results to be shared with Caltrans as a way to promote use of the products in the region. Are the tool results consistent with agency expectations and predictions from other models? Overall, the reliability results were consistent with agency expectations. For example, it was not surprising to Caltrans representatives that the L02 analysis showed that weather and incidents were the biggest reliability factors on I-5 in Orange County. SCAG and Caltrans representatives cited a rule of thumb that 50 percent of congestion delay is recurring and 50 percent nonrecurring, but they noted that it would be much better to measure reliability directly. In this sense, benefit-cost results that showed the total value of reliability benefits as roughly 30 194
percent of mobility benefits were unexpected. However, it made sense to agency representatives that reliability issues increased with congestion. Overall, they liked seeing reliability benefits added to benefit-cost analysis. Do the L02 procedures and use cases help identify the contributions of factors to reliability and better describe reliability conditions on the facility? SCAG and Caltrans representatives reacted positively to the cumulative distribution function (CDF) graphs and percent contribution tables as ways to summarize factors contributing to reliability. Representatives from both agencies noted that these tools would be useful to include in the Southern California CSMPs. Caltrans representatives who were not involved in the project found the CDF graphs difficult to understand without some explanation of their meaning. SCAG and Caltrans stakeholders noted that the graphs would be easier to understand with speeds rather than travel rates plotted on the x-axis. In addition, they wanted to see particular speed thresholds plotted on the graph, such as at 45 mph and 35 mph. Transportation decision makers are simply more accustomed to seeing speed than travel rates. Caltrans representatives thought that the CDF curves could help diagnose reliability problems and help design strategies to address those problems. They might also be used to operate the facility more efficiently. For example, the I-5 CDF curves suggest that bad weather in combination with high congestion has very large impacts on reliability. Changeable message signs (CMS) could provide traveler warnings when these conditions occur on the facility. Caltrans representatives liked the causal factor chart and wanted to understand the measures used and how the chart was developed. They particularly appreciated that the factors added to 100 percent to cover all conditions on the facility. Stakeholders preferred to have work zones and planned lane closures identified as another factor rather than included in special events. They added that accidents and reliability issues can occur during nighttime closures. Are the guidelines found in L05 helpful in choosing goals, in setting levels, and in picking strategies? The study team was not able to choose reliability goals using the L05 guidelines within the time frame of the L38 project. SCAG believes that the guide will be helpful in articulating the issue of system reliability, developing a framework for incorporating reliability into its planning and decision-making processes, and communicating the results to the stakeholders, members of the public, and decision makers as part of its next RTP, which will be developed over several years. In addition, the reliability objective tree may help Caltrans set objectives for operations strategies and incorporate reliability into policy statements. How willing were they to incorporate the results into programming decisions in the near future? Caltrans uses a variety of performance measures to select projects, such as mobility, safety, and the environment. Caltrans representatives recognized the value of including reliability in decision making and thought reliability could be useful as one measure among many for choosing operations projects to program. Reliability may help to promote managed lane projects, 195
