An Update on Public Transportation's Impacts on Greenhouse Gas Emissions (2021) / Chapter Skim
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Pages 47-57
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47 Transit Multiplier Methodology This appendix provides the full methodology for the model used to develop the transit multiplier for this project. This method and its application in the public transportation GHG analysis are summarized in the body of the report and Appendix A.
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48 An Update on Public Transportation's Impacts on Greenhouse Gas Emissions • Parcel-level land-use data with detailed land-use classifications; from these, detailed measures of land use mix can be computed. • A geographic information system (GIS)
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Transit Multiplier Methodology 49 sign and a statistically significant relationship to the outcome variables. Table B-2 presents the definition and descriptive statistics for all the endogenous (outcome)
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50 An Update on Public Transportation's Impacts on Greenhouse Gas Emissions multiple, interacting variables (Grace 2006)
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Transit Multiplier Methodology 51 errors and inefficient regression coefficients. MLM overcomes these limitations, accounting for the dependence among observations and producing more accurate coefficient and standard error estimates (Raudenbush and Bryk 2002)
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52 An Update on Public Transportation's Impacts on Greenhouse Gas Emissions across the United States can compute their own multipliers, it was decided not to use these data reduction techniques. In addition, all efforts have been made to have a parsimonious model with great explanatory predictive power.
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Transit Multiplier Methodology 53 in the multilevel analysis. In terms of the goodness-of-fit measures, piecewise SEMs do not have an equivalent to the Tucker–Lewis index or comparative fit index.
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54 An Update on Public Transportation's Impacts on Greenhouse Gas Emissions On the other hand, household income is negatively and significantly correlated with transit trips. This is mainly due to the fact that households with higher income prefer to use their own vehicles rather than using other modes such as transit.
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Transit Multiplier Methodology 55 By plugging in the coefficient values, this direct effect can be simplified to: [0.001 × (−2.882 + (0.002 × (transit passenger miles per capita – 130.05)
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56 An Update on Public Transportation's Impacts on Greenhouse Gas Emissions can use the average or range of the multiplier for the entire sample to estimate the total effect of transit on VMT from the direct effect. To recapitulate, transit reduces automobile travel in two different ways: directly when a traveler shifts a trip from automobile to rail or bus, and indirectly when it creates more accessible land use and reduces automobile ownership in an area.
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Transit Multiplier Methodology 57 model estimated in that report (which should not let the impact of land use on VMT vary across urbanized areas, yet the authors were somehow able to do so) , the main drawback of it is related to aggregation bias, which might lead to the "ecological fallacy" -- the conclusion that what is true for the group (i.e., UZAs)
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