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SECTION 2
Does TOD Housing Reduce Automobile Trips?
TOD has attracted interest as a tool for promoting smart Similarly, many proposed TOD projects have been halted
growth, leveraging economic development, and catering to abruptly or redesigned at lower densities due to fears that
shifting market demands and lifestyle preferences. Part of the dense development will flood surrounding streets with auto
appeal TODs hold is they behave differently from conven- traffic. Part of the problem lays in the inadequacy of current
tional development patterns. People living and working in trip generation estimates, which are thought to overstate the
TODs walk more, use transit more, and own fewer cars than potential auto impacts of TOD. ITE trip generation and
the rest of their region. TOD households are twice as likely parking generation rates are the standards from which local
to not own a car, and own roughly half as many cars as the traffic and parking impacts are typically derived, and impact
average household. At an individual station TOD can in- fees are set. Some analysts are of the opinion that there is a
crease ridership by 20% to 40% and up to 5% overall at the serious suburban bias in the current ITE rates. Typically,
regional level. Residents living near transit are 5 to 6 times empirical data used to set generation rates are drawn from
more likely to commute by transit than other residents in suburban areas with free and plentiful parking and low-density
their region. Self-selection is a major contributor to the ben- single land uses. Moreover, ITE's auto trip reduction factors,
efits of TOD, meaning that people choosing to live in a TOD to reflect internal trip capture, are based on only a few mixed-
are predisposed to use transit (Cervero, et al., 2004). use projects in Florida; there has been little or no observation
Given their performance characteristics, TODs present an of actual TODs. The end result is that auto trip generation is
opportunity to accommodate increased density without likely to be overstated for TODs. This can mean that TOD de-
many negative impacts associated with the automobile. While velopers end up paying higher impact fees, proffers, and
research clearly points to how TODs perform differently, the exactions than they should since such charges are usually tied
body of information on TOD travel characteristics has yet to to ITE rates. Smart growth requires smart calculations, thus
have an impact on industry guidance for projects near major impact fees need to account for the likely trip reduction
transit stations. effects of TOD.
This research seeks to bridge one of the widest knowledge
gaps on the effects of TOD on travel demand: automobile trip
Study Projects
generation rates for residential TODs. Empirical evidence on
vehicle trip generation can inform the setting of parking re- This study aims to fill knowledge gaps by compiling and
quirements for projects near major transit stations. Despite analyzing original empirical data on vehicle trip generation
the existing body of research and supportive local develop- rates for a representative sample of multi-family housing
ment, codes developers and financial institutions still tend to projects near rail transit stations. This was done by counting
prefer conventional parking ratios in TODs. As a conse- the passage of motorized vehicles using pneumatic tubes
quence most TODs are oblivious to the fact that a rail stop is stretched across the driveways of 17 transit-oriented housing
nearby and as a result, their potential benefits (e.g., reduced projects of varying sizes in four urbanized areas of the country:
auto travel) are muted. Structured parking in particular has a Philadelphia/N.E. New Jersey; Portland, Oregon; metropoli-
significant impact on development costs and is prohibitively tan Washington, D.C.; and the East Bay of the San Francisco
expensive in most markets. Lower TOD parking ratios and Bay Area (Figure 2.1). Rail services in these areas are of a high
reduced parking could reduce construction costs, leading to quality and span across four major urban rail technologies:
somewhat denser TODs in some markets. commuter rail (Philadelphia SEPTA and NJ Transit); heavy
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Figure 2.1. Case study metropolitan areas.
rail (San Francisco BART and Washington Metrorail); light rail stations can boost transit's commute mode share by as
rail (Portland MAX); and streetcar (Portland). Case study sites much as 4% (Cervero, 1996); and 3) car-shedding (i.e., the
were chosen in conjunction with the H-27A panel. tendency to reduce car-ownership when residing in efficient,
The most current ITE Trip Generation Manual (7th Edition) transit-served locations) (Holtzclaw, et al., 2002).
includes trip generation data for nearly 1,000 land uses and For studying traffic impacts of multi-family housing near
combinations. The primary focus of this research is on resi- rail stations, we selected mainly multi-family apartments
dential housing (ITE, 2003). The aim is to seed the ITE manual (rental) and in one instance, a condominium project (owner-
with original and reliable trip generation data for one impor- occupied). Table 2.1 provides background information on the
tant TOD land useresidential housingwith the expectation selected TOD-housing projects and Figures 2.2 through 2.5
that other TOD land uses and combinations (e.g., offices) will show their locations within metropolitan areas and photo
be added later. There is hope the research prompts local offi- perspectives of the sampled housing projects.
cials to challenge how they evaluate the likely traffic impacts Housing projects ranged in size from 90 units (Gresham
of housing near major rail transit stations as well as the Central Apartments) to 854 units (Park Regency). Most proj-
parking policies for these projects. The research, moreover, ects were garden-style in design, around three to four stories
complements several other studies presently underway that in height. The sampled Washington Metrorail projects,
aim to further refine trip generation rates to account for the however, tended to be much higher as revealed by the photo
trip-reducing impacts of mixed-use development (typically images, with the exception of Avalon near the Bethesda Metro-
through internal capture). rail station. The average number of parking spaces per proj-
The trip-reduction effects of transit-oriented housing are ect was around 400, yielding an average rate of 1.16 spaces per
thought to come from three major sources: 1) residential self- dwelling unit. The only nonapartment project surveyed was
selection: for lifestyle reasons people consciously seek out Wayside Plaza in Walnut Creek, near the Pleasant Hill BART
housing near major transit stops for the very reason they want stations, a condominium project. Six of the surveyed housing
to regularly take transit to work and other destinations; stud- projects had ground-floor retail and/or commercial uses,
ies in California suggest as much as 40% of the mode choice however all were primarily residential in nature (i.e., more
decision to commute via transit can be attributed to the self- than 90% of gross floor area was for residential activities).
selection phenomenon (Cervero, 2007); 2) the presence of Another selection criterion was the project not be immedi-
in-neighborhood retail sited between residences and stations ately accessible to a freeway interchange. All of the sampled
that promote rail-pedestrian trip-chaining; an analysis of the projects were more than 500 feet from a freeway entrance; five
American Housing Survey suggests the presence of retail near were situated within a quarter mile of a freeway on-ramp. The
