Cover Image

Not for Sale



View/Hide Left Panel
Click for next page ( 14


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 13
13 High-quality public transit also has the ability to influ- before moving to the area (13). TCRP Report 128 examined ence urban development. High-quality transit reduces the TODs in four metropolitan areas and found that TOD hous- need for more road lanes and large parking lots. Higher land ing produced considerably less traffic than conventional prices around transit stations promote more compact devel- development. TODs surveyed averaged 44% fewer vehicle opment as residents and businesses economize on space. In trips on a weekday than predicted by the ITE Trip Genera- addition to market forces, good urban planning also dictates tion manual, the standard resource for estimation of vehicle that development should be focused around transit nodes trips in conventional developments (8). Many more stud- to maximize the use of transit. Thus, transit and compact ies have examined the impacts of TOD on residents' travel development tend to beget one another in a virtuous feed- behavior, the potential for TOD to shift travel patterns at a back loop. regional or national scale, and design characteristics of TOD. TCRP Report 128 contains an extensive literature review By encouraging compact development, transit indirectly and bibliography. affects even the travel patterns of people who do not take transit. Compact communities typically allow people to travel shorter distances to get from place to place, as homes EMISSIONS FROM AGENCY OPERATIONS and businesses are closer together. Those who do drive can drive fewer miles. Compact communities also tend to be In addition to displacing emissions from private vehicles, friendly places for walking and biking, which eliminate transit produces its own GHG emissions. These emissions vehicle trips altogether; and areas rich in transit tend to have come from the tailpipes of transit vehicles and nonrevenue lower rates of car ownership than other areas. These impacts vehicles owned by the agency, from office buildings and of transit on the travel patterns of nontransit riders have maintenance yards, from transit stations and other facilities, been demonstrated in various urban contexts. A 2000 paper from construction of transit systems, and from the travel by Holtzclaw reviewed six previous studies that compared patterns of transit agencies' employees. The following sub- travel patterns in major urban areas in the United States and sections discuss these sources of emissions in greater detail. abroad. The studies showed that impacts of transit systems Strategies to reduce emissions from agency operations are on travel patterns were greater than miles traveled on transit discussed in chapter four. alone by a factor of 1.4 to 9. Older transit systems tended to have greater impacts than newer transit systems (11). The Transit Vehicles and Fuels sum of such impacts on travel patterns is substantially less driving in compact communities. Tailpipe emissions from transit vehicles are the primary source of GHG emissions from transit. All transit vehicles Transit-oriented development (TOD) is a type of compact are responsible for some GHG emissions. Vehicles pow- development explicitly associated with transit. TOD is usu- ered by conventional fuels and most alternative fuels emit ally characterized by above-average densities, orientation to GHGs from their tailpipes. Vehicles powered by electric- pedestrian activity, and easy walking access to a major pub- ity are responsible for some GHGs emitted from electric lic transit station or stop. The objectives of TOD can include plants. In 2006, U.S. transit vehicles used 735 million gal- the following: lons of diesel fuel (see Table 1). Combusting that amount of diesel produces roughly 7.4 MMtCO2, or about as much Increasing opportunities for travel by transit, emitted by transportation in the state of New Hampshire Attracting new riders to transit, each year (8 ). Shifting transit access trips from driving to walking, Reducing automobile activity associated with new TABLE 1 developments, and DIESEL FUEL USE BY PUBLIC TRANSPORTATION, 2006 Reducing energy use and associated emissions from Mode Million Gallons transportation. Bus 536.7 TODs can exist in urban or suburban areas; mix office, Commuter Rail 78.6 retail, and residential space; and provide access to rail or Paratransit 86.8 high-quality bus service (12). Ferry Boat 33.5 A significant body of research is devoted to the impact Other 0.2 that TODs have on the travel habits of residents. Most stud- ies find that residents of TODs use transit more and drive Total 735.1 less than their counterparts in other types of developments. (Source: Neff, 2008 Public Transportation Fact Book, Part 2: Residents of TODs typically drive fewer miles to work than Historical Tables, APTA, Washington, D.C., June 2008).

OCR for page 13
14 In addition to the emissions from energy used to propel Although tailpipe emissions account for the majority of transit vehicles, the vehicles themselves are also sources of life-cycle emissions for each mode examined, nontailpipe GHG emissions "upstream" from the point of use. The man- emissions from vehicles can be substantial. An average tran- ufacture of transit vehicles requires raw materials includ- sit bus emits 1,240 metric tons of CO2 equivalent (MtCO2e) ing glass, rubber, plastics, steel, and other metals. Energy from the tailpipe in its 12-year lifetime. The manufacture, is needed to extract, process, and assemble these materials. repair, and maintenance of the bus over its lifetime produce Emissions associated with these steps are known as embod- another 183 MtCO2e, or an additional 15%. An average ied emissions. Materials and energy are also required to sedan emits 69 MtCO2e from the tailpipe in its lifetime. The maintain vehicles throughout their lifetimes, as they require manufacture, repair, and maintenance of the sedan produce tune-ups and new parts. At the end of a transit vehicle's another 13 MtCO2e, or an additional 19% (14). useful life, energy is required to disassemble and scrap the vehicle. Each of these processes within the life cycle of the Facilities, Stations, and Maintenance Yards vehicle uses carbon-based energy and is therefore respon- sible for GHG emissions. Transit agencies use energy not only in transit vehicles, but also in all buildings and structures that they maintain. Every A research team at the University of California, Berkeley, transit agency requires office facilities, which consume conducted an extensive analysis of GHG emissions from each energy for heating, cooling, lighting, and computers and life-cycle component of auto, bus, light-rail, and heavy-rail electrical equipment. Office facilities also consume materi- transportation. Figure 8 shows the relative life-cycle impacts als (particularly paper) that require energy to produce, trans- of cars, SUVs, pickups, and buses, as calculated in that study. port, and discard. Larger transit agencies and agencies with A typical bus running during peak hours, with 40 passengers, rail transit also maintain transit stations that require heat- has the lowest emissions per passenger mile traveled. A typi- ing, cooling, lighting, and energy for electrical equipment. cal bus running during off-peak hours, with only five passen- Finally, transit agencies require maintenance yards to keep gers, has the highest emissions of GHGs per passenger mile up their fleets of buses and trains. Any energy used in these traveled. The study assumed average passenger loads of 1.58 maintenance yards that is derived from carbon-based fuels for sedans, 1.74 for SUVs, and 1.46 for pickups. results in GHG emissions. FIGURE 8 Vehicle and infrastructure life-cycle emissions by mode (grams of CO2e per passenger mile traveled) (Source : Chester, Life-cycle Environmental Inventory of Passenger Transportation in the United States, Institute of Transportation Studies, Dissertations, University of California, Berkeley, 2008.)