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Urban Transit Use and Emissions Data

Policies that encourage increased use of more efficient transportation modes, such as public transportation and high-occupancy private autos, are often considered one of several possible tools in the “sustainable development” toolbox. However, no definitive quantifications are yet available regarding the potential benefits that could be derived from such policies in terms of potential reductions in greenhouse gas (GHG) emissions.The transit lab team has papered a preliminary model that takes an important step in quantifying these effects. In order to do so, significant effort and thought was required to compile an integrated database capable of addressing these issues.

Given that mode choice takes place in a complex environment with both competing and complementary services, the developed empirical model must effectively capture the range of transportation modes available in urbanized areas. In addition, the model must include travel choice variables and variables relating to policies and regulations aimed at reducing CO2 emissions.  Therefore, it is necessary to integrate multiple data sources in a consistent manner to enable the estimation of robust and rich empirical models.

A study done by the transit lab team focuses on urbanized areas in the United States. The data of interest fall into three general categories relating to transit supply and use, roadway supply and private automobile use, and urban geography. As a result, the main sources of data used in their study included the following:

  • 2000 US Census (US Census Bureau, 2010) and Public Use Micro-data Samples (PUMS) from that decennial census (US Census Bureau, 2010). These data correspond to the US Census Bureau defined “urbanized areas” (UZAs) and are collected on a time-cycle of 10 years.
  • 2003 National Transit Data (NTD) (2010), a database produced by the US DOT Federal Transit Administration (FTA). These data correspond to the US Census Bureau defined UZAs and are collected annually.
  • 2003 Federal-Aid Urbanized Area (FAUA) database (Federal Highway Administration, 2010b) produced by the USDOT Federal Highway Administration (FHWA). These data correspond to the FHWA defined “federal-aid urbanized areas” (FAUAs) and are collected annually.
  • 2001 National Household Travel Survey (NHTS) (US Census Bureau, 2010). These data correspond to the US Census Bureau defined UZAs and are collected on a time-cycle of 5 to 8 years.
  • 2000 Inspection and Maintenance Overview (I/M) (Wilson, 2000), commissioned by the Equipment and Tools Institute (ETI). These data, collected annually, are summarized at the state level and specify within each state what the different regulations are if they vary.
  • 2002 National Emissions Inventory Data (NEID) (US EPA, 2012), collected and calculated by the US Environmental Protection Agency (EPA). These data, released approximately every five years, are calculated at the county level.

Variables of Interest and their sources can be seen in the tables below.