ITE Journal April 2018 - 44
residential projects with assigned spaces where maybe one third
of the resident spaces are occupied during the day, and daytime
visitors and contractors have to park in specially designated spaces
or cannot find parking.
It should be noted that zoning requirements for residential
parking implicitly assume that parking spaces are assigned (unless
the zoning text specifies non-assigned parking requirements) and
consequently that visitors/contractors need to have a separate
parking supply. Zoning codes should therefor allow lower parking
ratios in situations where developers do not provide assigned spaces
to take into account the constant absence of some of the cars and
the sharing between residents and visitors/contractors.
Shared parking is a tool that allows us to increase our land-use
efficiencies, improve the economics of our developments and
enhance the sustainability of our built environment. The benefits
in terms of parking supply can be significant, but they also vary
substantially depending on the mix of uses and the magnitude of
each use. To quantify the savings in parking spaces one needs to
calculate the parking demand of each development component
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i te j o urn al
by time period to determine the overall peak demand and figure
out the critical time period. Zoning codes should require shared
parking analyses based on the percentage presence of parkers for
each use and for the critical time periods. It is not recommended to
use a flat percentage to quantify the benefits of shared parking.
Shared parking can be beneficial in TODs; however, its benefits
tend to be more limited, for two reasons: First, residential parking
ratios are lower in a TOD and the percentage of cars that remain
in the parking facility are higher (often in the range of 60 to 65
percent), thus reducing the amount of parking spaces vacated
during working hours. Second, if the residential spaces are to
be shared with transit commuters, the timing would only work
for transit stations that are relatively close to downtown, i.e. in
locations where the transit commuters don't arrive too early.
Shared parking between residential and office users in a TOD is not
restricted by the timing issue.
The assignment of parking spaces to individual users in
residential developments is a major obstacle to more efficient
parking, including shared parking. Changing travel behavior
related to declining interest in auto ownership and use, the
introduction of shared cars and transportation network companies
will tend to reduce auto ownership and make it easier to move away
from assigned or reserved parking spaces. Embracing this change
and discouraging assigned parking spaces will allow us to improve
our built environment and land-use efficiencies. itej
1. Smith, Mary S. Shared Parking. Second Edition. Washington, DC, USA:
ULI - the Urban Land Institute and the International Council of Shopping
2. Institute of Transportation Engineer (ITE). Parking Generation. 4th Edition.
Washington, DC, USA, 2010.
Georges Jacquemart, P.E., AICP is a principal of
BFJ Planning in New York City, NY, USA. He started
his career in the field of transportation planning and
traffic engineering more than 40 years ago with Alan
M. Voorhees & Associates. He holds graduate degrees
in planning and engineering from Stanford University
and from the Federal Polytechnic Institute of Lausanne, Switzerland.
Georges was an adjunct professor at NYU and Pratt Institute, NY. He
is a member of ITE and lives, works, walks, bicycles, and drives in