Assessing and Comparing Environmental Performance of Major Transit Investments (2012)

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

. 95 6.0 Next Steps and Issues for Further Research This research has provided an overview of the use of different metrics of environmental performance, but has left a number of issues unaddressed. These can be grouped into next steps for implementation, and issues for further research.  6.1 Next Steps for Implementation The following issues will need to be addressed by decision makers and others who chose to apply these metrics.16 • Which metrics (if any) will an individual agency use for their own project evaluation purposes? How will they be used to inform project decision-making, including weighting them in relation to other measures of performance? - • Which metrics (if any) will be used for comparative evaluation of projects, and how will they be incorporated into the evaluation and reporting framework? What weights would be set for each metric within the environmental performance category, and how would this overall category be weighted in comparison to other categories? • If a GHG metric is selected, will GHG be calculated based on regional emission factors, or national average factors? ICLEI’s protocol for development of GHG inventories by local governments specifies the use of local/factors,17 • If an air quality metric is selected, which pollutants are included? Are emissions from powerplants from electricity generation included? Again, if the metric is applied although decision makers would not necessarily need to be consistent with this practice. 16 FTA’s January 25, 2012 Notice of Proposed Rulemaking and accompanying Proposed New Starts/Starts Policy Guidance address some of these issues. For example, the policy guidance proposes the specific environmental metrics to be examined, how they will be combined and weighted, general methods for calculating these metrics, and the use of national rather than regional emissions, energy, and GHG factors. Details of data sources and calculation methods remain to be developed. 17 ICLEI (2009). International Local Government GHG Emissions Analysis Protocol (IEAP), Version 1.0.

96 comparing projects in different regions of the country, are national or regional emission factors used?  6.2 Issues for Further Research Issues that warrant further research – some shorter-term and easier to address, others longer-term in nature – include the following: • What are the most appropriate energy and GHG emission factors, particularly for future energy use and emissions from all types of transit vehicles (including electricity generation)? • What is the full range of energy use and GHG emissions from transit construction? (This may be addressed by research underway for FHWA). • Can the Exposure Index and/or Health Benefits Index be further developed so that they are useful for transportation project and/or plan evaluation, considering health effects? • How do different models of nonmotorized access mode choice affect the reliability of access mode choice forecasts? To what extent do transit projects induce nonmotorized trips in addition to those accessing the transit project (e.g., by allowing households living in transit station areas to have fewer vehicles)? • Can systems-level forecasting methods (considering regional transportation and land use systems) provide information on the environmental benefits of projects that is sig- nificantly different than that provided by project-level methods that simply compare the project versus no-project alternative in isolation from other changes? • To what extent are the environmental benefits of transit increased by the “trip not taken”? That is, to what extent are our current evaluation methods not capturing the benefits of more compact development and associated changes in travel patterns (including changes such as increased walking and bicycling for short trips, in addition to new transit trips)? This concept is also known as the “land use multiplier.” Some research is underway to expand our understanding of this issue through TCRP H-46, Quantifying Transit’s Impact on GHG Emissions and Energy Use: The Land Use Component, but ongoing research is likely to be required because of the complexity of the topic and the variability of the relationships in different situations. • What are the advantages, drawbacks, and implications of evaluating the environmen- tal benefits of a project as part of a regional plan (i.e., in comparison to a no-plan or alternative plan), rather than in isolation from other changes?