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36 nontransit trips. This technique requires matched data on APTA's methodology offers three approaches to calculat- alternative mode and length of trip for each rider. ing the benefits of reduced congestion: Based on this analysis, the transit agency estimated that Applying a mode shift factor directly to data reported the iXpress service eliminates 1.5 million km (932,000 mi) in the TTI Urban Mobility Report--This approach is of auto travel annually, and thereby displaces 500 metric the simplest. It requires only that the transit agencies tons of GHG emissions through travel mode shift. The net correct the mode shift factor that TTI uses to calculate impact of the iXpress, accounting for an increase in emis- the transit congestion reduction benefit (0.8). Agencies sions of transit vehicles from the former conventional bus should use mode shift factors specific to their regions. service to the BRT service, is a reduction of 450 metric tons Extrapolating from data in the Urban Mobility of GHG emissions annually. Report--This is a more sophisticated estimation tech- nique requiring the application of basic statistical mod- Although empirical data can be used to estimate emis- eling to a time-series of data in the Urban Mobility sions displaced by existing transit service, analyzing pro- Report. posed improvements requires the use of ridership forecasts. Applying regional travel demand models --With At the time of the analysis, the Region of Waterloo had not this approach, a regional travel demand model is run fully implemented all technology measures on the iXpress. assuming no transit service, and the increase in vehicle Based on projected increases in ridership, the transit agency hours of delay and/or fuel consumed in congestion is expects that the mode shift effect of the service will rise to measured. As with the modeling approach for travel 750 metric tons of GHGs reduced annually 1 year after full mode shift, the results of this approach depend on the implementation of all technologies (51). sophistication of the model, and substantial resources may be required to run the model. CONGESTION MITIGATION The recent CALPIRG study used TTI's figures for fuel savings without adjusting for regional mode shift factors. Transit agencies can use several different techniques to esti- That study produced estimates of GHG emissions reduced mate the additional GHG emissions reduced by their service by individual transit agencies across the country. Where a through mitigation of congestion. Most analyses rely on data city had more than one transit agency, the benefits of reduced from the TTI's annual Urban Mobility Report, which pro- congestion were divided among agencies using each agency's vides congestion data for 85 metropolitan areas in the United share of regional PMT (16 ). Benefits might also be divided States (9). The Urban Mobility Report includes an estimate using the share of regional passenger trips. (CALPIRG's for each urban area of the amount of gasoline saved by tran- results for individual transit agencies are provided in Appen- sit's reduction in congestion on roadways. dix C.) Both the ICF and SAIC studies, which only calculated FIGURE 16 iXpress rider survey results--Mode used prior to availability of iXpress. (Source : Hellinga and Cicuttin, "Impacts of New Express Bus Service in Waterloo Region," submitted for the Transportation Association of Canada Annual Conference, Session, Integrating Transit Service into Communities, Saskatoon, Saskatchewan, Oct. 1417, 2007, p. 16).