Shared Parking
eBook - ePub

Shared Parking

Third Edition

Mary Smith

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  1. 150 pages
  2. English
  3. ePUB (mobile friendly)
  4. Available on iOS & Android
eBook - ePub

Shared Parking

Third Edition

Mary Smith

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Book preview
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About This Book

Avoid unnecessary costs and traffic by accurately estimating the parking requirements for mixed-use projects according to the types of tenants they will attract. Now in its third edition, this authoritative book has been updated throughout by author Mary S. Smith, a leading parking expert, in collaboration with parking professionals and developers. It includes many additional land uses, and revised parking ratios, and addresses trends such as increased use of ride sharing services and scooters. This book is essential for developers, planners, government agencies, consultants, and engineers. Separately available is the Shared Parking book with Excel model version (ISBN 978-0-87420-443-8) which lets you plug in your project's land uses and calculates the number of parking spaces needed.

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Shared parking is the use of a parking space to serve two or more individual land uses without conflict or encroachment. The ability to share parking spaces is the result of two conditions:
  • Variations in the accumulation of vehicles by hour, by day, or by season at the individual land uses; and
  • Relationships among the land uses that result in visiting multiple land uses on the same automobile trip.
Although this methodology for shared parking analysis was developed in the early 1980s,1 the concept of shared parking was already well established: a fundamental principle of downtown planning from the earliest days of the automobile—indeed from the days of the horse and buggy—has always been to share parking resources rather than to allocate parking for each use or building. The resurgence of many central cities resulting from the addition of vibrant residential, retail, restaurant, and entertainment developments continues to rely heavily on shared parking for economic viability. Shopping centers have benefited from the addition of significant dining and entertainment venues, which draw pedestrian traffic (and parking) at other times of the year than the holiday shopping season, taking advantage of shared parking between retail and dining/entertainment uses. In addition, mixed-use projects in many different settings have benefited from shared parking.
Parking is a key element of any site development plan. Parking can consume 50 percent or more of the building and land area of a development. An oversupply of parking can result in excess storm drainage impacts and unnecessarily high expenses (as of 2019, surface stalls can cost $3,500 to $6,000 per space, above-grade structured spaces $15,000 to $35,000, and underground parking spaces $30,000 to $50,000 or more). Insufficient parking can result in the intrusion of parking into neighborhoods or adjoining properties, excessive vehicle circulation, and unhappy users. Ultimately, great parking alone won’t make a mixed-use project successful; however, inadequate or poorly designed parking can limit its potential success.
The most anti-sustainable approach of all is not to consider shared parking!
The triangular development in figure 1-1 has a “front row” of individual buildings including a pharmacy and two fast-food restaurants (toward the left in the photo); a middle row of strip retail (several of which are restaurants); and a third group of offices to the right that are primarily medical uses.
Reportedly, the local government required this design by forcing the developers to provide the two intermediate roads through the project, which extend for more than a mile through other commercial developments to the south.
A person who visits a doctor in the office buildings would drive and park at the pharmacy to pick up a prescription and then drive and park at the strip center to have lunch or pick up dry cleaning. If the exact same uses had been provided in a single two-story building, with the offices on the second floor over the retail at grade, the vehicle would have been parked only once. With shared parking between these uses, the site could have accommodated at least 50 percent more of each use with adequate parking. This might have slowed the creeping commercial development of farmland along this corridor that occurred over the past 25 years.
FIGURE 1-1 A Wasted Opportunity for Shared Parking
An increasing concern today is the potential for future reductions in parking demand. Ride-hailing services offered by transportation network companies (TNCs) such as Uber and Lyft are already affecting parking requirements for many land uses, and significant potential exists for reduction in parking required if autonomous vehicles (AVs) become common.
The key goal of shared parking analysis, then, is to find the balance between providing adequate parking to support a development from a commercial viewpoint while minimizing the negative aspects of excessive land area or resources devoted to parking and the potential for declining parking demand in the future. Mixed-use developments that share parking result in greater density, better pedestrian connections, and, in turn, reduced reliance on driving, typically because multiple destinations can be accessed by walking. Higher-density development, especially on infill sites in urban areas, is also more likely to support alternative modes of travel, including transit and carpools. Ironically, a critical element of pedestrian-oriented districts is adequate parking.
Concern for the negative impacts of growth stimulated a search for better ways to develop land. “Smart growth” is a collection of planning principles and strategies designed to facilitate economic development, strong communities, and environmental health.2 A particular focus of smart growth is to reduce sprawl. Smart growth projects typically are designed to create transportation options and reduce driving, especially for short trips. Walkable live/work/play environments, located near established mass transit connections and infrastructure in the city are central to the concept. Some communities are questioning the economic costs of abandoning infrastructure in the city only to rebuild it further out.3 A recent publication by the American Planning Association4 discusses the fiscal impacts for the community of urban density versus suburban low-density development and concludes as follows:
  • Smart growth generally costs up to one-third less for upfront infrastructure.
  • Smart growth saves an average of 10 percent in ongoing services such as police, ambulance, and fire service costs.
  • Smart growth generates 10 times more tax revenue per acre.
A key principle of development today is known as “placemaking,” which more strongly ties people to places. Placemaking typically focuses on the public spaces linking land uses to “capitalize on a local community’s assets, inspiration, and potential, with the intention of creating public spaces that promote people’s health, happiness, and well-being.”5 ULI has recently undertaken an initiative known as the Creative Placemaking Project to “help build strong, healthy cities by promoting the integration of arts and culture in community revitalization.”6
Another significant development type today is transit-oriented development (TOD), which seeks to cluster development near transit stations. With housing located within walking distance of rail transit, some trips and, in turn, some parking spaces can be eliminated.
Shared parking is a critical factor in the success of all these development approaches, and thus the importance of shared parking will continue to grow in future years. This report aims to provide parking consultants, planners, engineers, developers, and agencies with tools to better quantify and understand how shared parking can be successful.


The widely accepted methodology for shared parking analysis was established in 1983 with the publication of the first edition of Shared Parking. In 2005, ULI and ICSC published a second edition, particularly to update and expand the land use categories and default factors. A decade later, the Parking Consultants Council (PCC) of the National Parking Association (NPA) proposed to ULI and ICSC that another update was due, given changes in society, transportation, and mixed-use development trends. The consensus was that the underlying concept and methodology are still viable but that an update of the default factors and addition of more land uses would be appropriate. Therefore, NPA’s PCC was appointed by ULI and ICSC to update the publication, with NPA managing the process of producing the document. Subsequent to the start of the project, the Institute of Transportation Engineers (ITE) joined the effort, with the intent to coordinate updates to both Shared Parking and ITE’s Parking Generation Manual7 (PGM, fifth edition, unless noted otherwise) database of observed parking ratios for individual land uses. Therefore, this third edition is truly a collaboration of the leading professionals in parking demand analysis as well as developers with a vested interest in “getting the number of parking spaces right.” One might call this the “just enough, no regrets” parking supply for mixed-use developments.
Concededly, the number of parked cars per unit of land use on a design day falls within ranges, depending on the mix, types, and strength of the tenants of each land use. The recommendations herein are the recommended parking supply for these individual uses separately and when combined in a mixed-use project, particularly when planning and designing parking well before the development is fully leased.
As with any guidelines, the base ratios and other recommendations herein are a starting point for analysis, subject to adjustment to reflect professional judgment, market conditions, and regulatory requirements.
FIGURE 1-2 Changes in Land Uses and Base Parking Ratios from Previous Editions
Note: Changes shown in bold. Blank cells indicate “not applicable.”


Chapter 2 discusses the principles of shared parking, as well as the methodology recommended herein, with business rules for determining ratios and adjustments. Chapter 3 discusses regional and scale recommendations that are critical to proper analysis.
Chapter 4 discusses the parking needs of individual land uses and the derivation of the default values. Chapter 5 discusses design of shared parking facilities while chapter 6 discusses operation and management of parking facilities for shared parking to succeed. Chapter 7 presents case studies using the updated Shared Parking Model (SP Model).
Chapter 8 discusses how local communities can incorporate shared parking in zoning ordinances.


This edition of Shared Parking significantly increases the number of land uses—from 20 to 32—for which recommended parking ratios are presented, and it subdivides some land uses into more refined categories while eliminating subdivisions of others. There are 44 different parking ratios recommended. These changes are summarized in figure 1-2.
No significant change in methodology has taken place; base ratios are provided for each land use based on a suburban location with little or no transit. This “big decision” at the beginning of the update process not only was based on the collective opinion of NPA’s PCC, but a group of interested ITE member-consultants also convened to discuss the need to update Shared Parking. It is simply impossible to develop other sets of base ratios, for example for a central business district (CBD) or TOD, because (a) enough data are simply not available to develop complete sets of ratios and (b) they would still need to be adjusted for local conditions, just with adjustment from the inherent driving ratio embedded in CBD and TOD ratios.
Instead, significantly more guidance is provided on how to do driving adjustments using U.S. Census Bureau data on vehicle ownership and journey-to-work data.
The SP Model also has a new subroutine that automatically calculates noncaptive ratios based on the presence of employees, hotel guests, and residents who will patronize retail/dining/entertainment (RDE) uses in the project. The user can adjust the percentage of those persons who will patronize other uses, or even override the default calculation, but the subroutine will replace fundamentally guessing at captive-market adjustments.
Readers should further be reminded that statistically valid studies of relatively few land uses herein for base ratios are published, much less the hourly and monthly adjustment factors, which are typically based on some studies and professional judgment. However, the successful application of the second edition of Shared Parking for 15 years as well as the consensus of the shared parking committees of PCC and ITE supports that this approach is the preferred methodology.
For retail, this update continues the second edition’s use of the recommended ratios from Parking Requirements for Shopping Centers (1999). At that time, it was the most well-documented study of parking demand ever, for any land use, in the judgment of NPA’s PCC. Although anecdotal reports exist of declines in parking demand of shopping centers caused by various factors, including e-retailing, ride hailing, and loss of department store anchors and name retail brands, t...

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