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Figure 8.11. Benefit-cost results for I-210 facility with C11 reliability estimate modified. 8.4 Implications for Decision Making Caltrans and SCAG originally chose to use microsimulation for modeling operational projects in the CSMPs because travel demand models tended to underestimate the mobility benefits. This is because traditional travel demand models are only able to look at individual links and unable to examine how relieving bottlenecks removes queuing upstream and shifts demand downstream. Perhaps then, it should not be a surprise that a link-based model like the L07 tool underestimates mobility benefits compared to microsimulation modeling. Does including travel time reliability impact the ordering of projects? It did not for the CSMP scenarios modeled in tests described above. However, the test results suggest that including travel time reliability can make a difference for projects with similar benefit-cost ratios. It may also make a difference for marginal projects. Is travel time reliability worth the trouble of modeling? The benefit-cost test suggests that one may be able to apply a 29 percent to 36 percent factor to account for travel time reliability. However, there was some variation between scenarios, and these results may not hold true for other facilities. Furthermore, the study team did not examine what would happen if travel time reliability benefits were estimated using FREEVAL-RL. This tool is likely to estimate higher mobility (and reliability) benefits because it is more similar to estimating the interaction between links (like a microsimulation model) than is the C11 tool. In addition, this discussion does not consider the communication aspect of being able to model travel time reliability. Original Benefits from CSMP Modified Reliability Benefits Scenario Project Cost 187
What should agencies do to include travel time reliability in project analysis? The study team suggests that agencies consider using a simple approach, such as the C11 tool, if they already have detailed approaches, such as microsimulation modeling, for estimating mobility benefits. If detailed approaches are not available, the FREEVAL-RL tool may be appropriate for modeling both the mobility and the reliability benefits. However, analysis with FREEVAL-RL is data- and time-intensive, as described in Chapter 7 of this report. 188
CHAPTER 9 Functionality Assessment and Research Outcome This section provides a summary assessment of the SHRP 2 products tested at the Southern California pilot site and describes the outcomes of the analysis. The study team began its assessment of technical functionality during tool testing. These observations are documented in detail in Chapters 5 through 7. The team spent considerable time learning how to use and calibrate the tools for its two study facilities. The study team made additional observations about tool functionality while conducting the benefit-cost analysis. For example, the team discovered that the C11 tool does not explicitly include average vehicle occupancy (AVO) as part of the user costs. It is assumed that AVO is implicitly included, but the tool would benefit from having an AVO input box. This and similar observations have been added to the tool limitations described at the beginning of Chapters 5 through 7. The assessment of agency and decision maker perceptions started with SCAGâs involvement in the tool testing. SCAG technical staff calibrated and ran the tools for one facility, while other study team members focused on the other facility. This allowed SCAG staff to have hands-on experience and provide agency perspectives. The SCAG staff involved in the SHRP 2 testing is also responsible for developing the next SCAG RTP. This allowed SCAG to consider how the guidelines found in L05 might be used for selecting goals for the RTP and how the results of the other tool tests might aid in setting reasonable thresholds. In addition, the study team conducted outreach throughout the project. Caltrans provided input into the selection of facilities, and one of the original candidate facilities was replaced based on this input. Projects had already been committed or programmed along the facility, so the pilot testing would have no chance of influencing project priorities. After the facility analyses were completed, the study team met with Caltrans district staff to share the tool testing results and benefit-cost analysis. Transportation planners and traffic operations engineers attended the meeting, so the study team was able to gather multiple perspectives. In addition, the meeting included decision makers responsible for operations projects. The study team sought input from other stakeholders through SCAG policy and technical committees. SCAG included a written update on the pilot testing in the consent calendar for its Transportation Committee. SCAG also provided its technical working group with an update on the project and the results of tool testing. This group has several stakeholders, including representatives from cities, counties, transportation commissions, subregional areas, Caltrans districts, and other interest groups. 189
