addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAs4. Estimate the user costs of asset failure. User costs are additional burdensplaced on passenger and goods movement due to asset failure. These costsmay include additional vehicle miles traveled, delay, congestion, etc.5. Estimate likelihood of asset failure. This step guides the user to thegeneration of year-by-year compound probabilities of failure, a function ofthe climate event likelihood and the likelihood that the asset will withstandthe event. Probabilities are generated for both the adaptation and nonadaptationscenarios.Unlike the approaches to determining the likelihood of asset failurerecommended in this document, the NCHRP 20-83(5) methodology mandates ahigh degree of precision – the approach is intended for use in a spreadsheetformat. To avoid an unrealistically precise failure probability, probabilitiespertaining to the climate event and the asset’s ability to withstand the eventcould be toggled to generate a range of likelihoods (resulting in a range of B/Cratios) or to determine the “tipping point” for taking action.6. Calculate agency benefits of the strategy. In this step, the agency benefits ofadaptation are calculated based on the inputs from Steps 2, 3, and 5.7. Calculate user benefits of the strategy. In this step, the user benefits ofadaptation are calculated based on the inputs from Steps 4 and 5. Userbenefits will increase over time as traffic volumes increase.8. Evaluate results. The guidebook suggests three options for expressing thebenefits:a. Calculate a benefit/cost ratio. The suggested applications of the B/Cratio include determining whether a given adaptation strategy is costeffective, comparing multiple adaptation strategies (ranked by ratio), orcomparing an adaptation action against another type of project (such ascapacity expansion).b. Determine a minimum benefit/cost ratio, above which a potentialstrategy becomes cost effective.c. Conduct a sensitivity analysis based on the probability and timing of anevent occurring. Toggling or creating multiple probability assumptionscan help agencies establish the tipping point for cost-effective strategies,as suggested above.Specifics for this approach, including formulae and an accompanyingspreadsheet template, are available by downloading the NCHRP 20-83(5) reportand guidebook. 2626 http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=2631 is the link toNCHRP 20-83(5). Spreadsheet template and final guide is planned for spring 2013, andhas not been posted at the time of this guide’s completion.Cambridge Systematics, Inc. 12-13