ITE Journal April 2018 - 40
Simple Way of Calculating Shared Parking Benefits
Shared parking is a strategy that allows us to optimize the use of our
parking resources and reduce the overall supply of parking needed.
This strategy has become more common as we see more mixed-use
projects coming on line. Shared parking takes advantage of the fact
that the parking demands of our various urban uses do not always
overlap or peak at the same time. However, shared parking is not
well understood, and many municipal officials are unsure on how
to deal with it. Since the savings in decreasing the required parking
supply can be substantial, it is important to develop a methodology
that quantifies the benefits in a reasonably accurate manner.
In the presence of parking garages, the benefits of shared
parking translate rapidly into very substantial financial savings.
A 15-20 percent reduction in garage spaces that cost in the order
of $30,000 per space can save enough money to significantly affect
the rental or leasing prices. Shared parking can therefore become
a tool to mitigate the ever-increasing cost of real estate. Part of
the financial savings gained from shared parking can be used to
enhance the appearance, comfort, and security of the garage.
The aerial photo in Figure 1 shows a commercial center with a mix
of offices, medical offices, restaurants, retail stores, day-care center,
fitness center, and hotel, built in the 1980s. Even at full occupancy,
the center has about 40 percent of its parking spaces vacant during
the peak activity period. This substantial excess of parking supply is
largely due to the fact that when it was originally approved, and also
in subsequent use changes, the parking requirements were cumulated
as per traditional zoning, without any credit for shared parking.
In most cases, shared parking benefits derive from varying parking
demand patterns within a regular weekday and possibly a weekend,
as opposed to varying seasonal patterns. Although seasonal
sharing benefits can be real for shopping centers and recreational
facilities, it tends to be the variation over a typical weekday and
Saturday that raises questions and requests for clarification. Since
the Urban Land Institute's 2005 publication Shared Parking, the
industry has benefitted from additional parking data published by
the Institute of Transportation Engineer's (ITE) Parking Generation
(2010), with more detailed hourly occupancies.1,2 And because ITE
publishes parking demand data for all users combined (as opposed
to employee cars, visitor cars, resident cars, etc.) and its data are in
many cases based on a significant number of underlying occupancy
surveys, there is a trend toward an analysis based on total parking
demand rather than by user group.
Tables 1 and 2 show two shared parking calculations for a
mix of retail and office uses. The tables show how to calculate the
shared-parking savings for a mix of office space and retail space.
The column titled "Peak Parking" shows the parking ratios and
the number of parking spaces that would need to be supplied, if
each use needed to address its own peak parking demand without
sharing. The ratios shown here may be the peak ratios provided
by ITE's Parking Generation, the ratios required by zoning, or
other peak ratios determined by the applicant. The subsequent
columns show for each critical time period the percent presence or
occupancy of the parkers for each use. These percentages are based
Bing screen shot reprinted with permission from Microsoft Corporation.
Why Shared Parking?
Figure 1. Commercial center with a mix of offices, medical offices, restaurants, retail stores, day-care center, fitness center, and hotel, built in the 1980s.
Ap r i l 2018
i te j o urn al