Shared Parking: Third Edition

By Mary Smith

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.

• Language: English
• Publisher: Urban Land Institute
• Release date: Mar 9, 2020
• ISBN: 9780874204490

Mary Smith

Mary Smith was born in Chicago, Illinois, but raised in Princeton, Illinois. She now lives in the hills of West Virginia. She is an avid reader, co-founder of Book Nerds Across America, and co-author of The Penalty Kill Trilogy. She goes nowhere without her cell phone or Kindle. Mary loves anything to do with Chicago Blackhawks, Patrick Sharp, and hockey related! She is also an avid Chicago Bears and Chicago Bulls fan.

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CHAPTER 1

Introduction

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.

OBJECTIVE OF THE THIRD EDITION

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.

ORGANIZATION OF THIS REPORT

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.

KEY CHANGES FROM SECOND EDITION

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, there has not been an adequate number of studies to document reductions, and some individual studies have found parking ratios on design days are holding constant. Shopping center owners are responding with a variety of approaches for successful centers, including adding dining and entertainment uses and fostering a feeling of community at centers. Retailers are having significant success with services offering online purchase with pickup in a store.

Therefore, the base parking ratios for shopping centers are unchanged. New ratios have been added for megamalls over 1 million square feet and over 2 million square feet based on consultant experience since the second edition was published. Both Parking Requirements for Shopping Centers and the second edition of Shared Parking indicated that a reduction of the parking ratio for these very large shopping centers was likely appropriate. Monthly and time-of-day factors for retail have been modified considerably to represent more recent shopping patterns.

New land uses have been added for supermarkets, pharmacies, discount superstores, and home improvement stores, all based on the PGM and deemed reasonably reliable for use as base ratios. It is noted that the pharmacy ratio is based on a reasonably strong database of those with drive-throughs. A ratio has also been added for discount superstores, despite the small sample size in the PGM.

Another land use added is daycare centers, which are an important amenity to many mixed-use projects. The ratios are based on a reasonably strong PGM database, with monthly and hourly factors based on NPA’s PCC professional judgment.

A number of new entertainment uses have also been added to the model. These uses are increasingly being added to shopping centers, converting them to RDE venues. For all these uses, the parking ratios, time-of-day, and monthly factors are based on one or more proprietary study, because the data in the PGM are not adequate or are too segmented into smaller categories to be useful. The factors herein are based on the experience, focused research, and judgment of NPA’s PCC. An investment in entertainment uses of this nature may justify using a consultant with access to attendance data and parking patterns for multiple projects, additional research specific to the proposed project using projections for attendance and staffing from the proposed tenant, or both. The new entertainment uses in Shared Parking include the following:

Amusement park/water park: The inclusion of these uses in modern shopping centers was pioneered by Triple Five, developer of the West Edmonton Mall, which has an enclosed water park, and Mall of America, which has an indoor amusement park. Others have emulated the concept, although typically at a lesser scale. Such uses may also be part of mixed-use projects.

Active entertainment uses: This category encompasses a wide variety of participatory and active uses, such as indoor ski venues, go-cart tracks, miniature golfing, and ice rinks.

Family entertainment centers: These uses are a little more densely occupied than active entertainment and oriented primarily to school-age children. They may have small rides, such as a carousel, as well as arcade games. Others may have role-playing or themed activities. The ratios are slightly higher than those for active entertainment. The key difference, however, is that operating hours end earlier in the evening and the seasonality follows the school year.

Adult active entertainment: These facilities, such as Dave & Buster’s, Punch Bowl Social, and Lucky Strike (bowling and billiards), combine active entertainment with a significant food and beverage component and particularly can have sports bars that have much longer stay than the quick food service at active entertainment or family entertainment uses. The density of persons is higher than either, because of the food and beverage aspect. The hours typically begin midafternoon on weekdays but earlier on weekends, and then they typically run later than other entertainment venues.

Museum/aquarium.

Public library.

Outdoor amphitheaters and park and destination open space: As part of placemaking, many projects have significantly more outdoor open spaces that may generate parking demand independently of the rest of the project. Outdoor amphitheaters may have lunchtime concerts or evening events that are particularly dense generators of parking demand. Similarly, park areas may be anchors of mixed-use projects and generate incremental parking demand not simply from within the project but from nearby residential neighborhoods, if not the entire region. A great example is Hemisfair in San Antonio, which is anchored by park space but has added food and dining venues, many in historic buildings, and a children’s theater, with plans for future office and residential uses.

World Waterpark at West Edmonton Mall in Edmonton, Alberta.

For restaurants, the ratios are based on detailed analysis of the raw data in the PGM; however, they are also supported by an in-depth study of more than 20 sites by one consultant in 2004. The ratios from the second edition have been modified slightly based largely on PGM, with the fine/casual dining ratio declining, the family restaurant ratio increasing, and the fast casual/fast food ratio being adjusted. For nightclubs, the second edition recommendations are retained in the third edition and are based on the judgment of NPA’s PCC, using estimates of visitor and employee density and typical time-of-day factors. There is, however, a significant variation in the density of patrons in nightclubs, and further investigation of similar clubs would be advisable where feasible.

The ratios for general cinema have been lowered slightly from the second edition, again based on the PGM. A new category of specialty theater has been added for the emerging trend to smaller auditoriums with a more limited number of screens then the megaplexes of the 1990s and with more amenities, including luxury seats, food and beverages, reservations, and the like. The specialty theater ratios assume nearly all the seats are occupied on the design day, which occurs in Late December.⁸ Cinema demand is highly variable from month to month and year to year, depending on the strength of the movies available. The base ratios are the best, collective judgment of NPA’s PCC as to how many spaces should be provided for this use.

However, the big change for this land use is the seasonality factors. The biggest movie season is now the entire month of December, rather than just between Christmas and New Year’s Day. This may affect shared parking in shopping centers with large multiplexes and may explain why PGM shows an increase in parking demand for shopping centers in December rather than a decrease, as many expected, because of changes in retail shopping in the past 10 years. It is yet more reason to do a shared parking analysis for a shopping center with more than 10 percent dining and entertainment.

The live theater ratios from the second edition are retained as well. Adequate data are not published on this use; therefore, the parking demand is based on assumed occupancy of seats on a design day, auto occupancy, and estimated employment.

For arenas, stadiums, and convention centers, the second edition ratios and default values are retained. All were based on a single very detailed study that is believed to be more reliable than the PGM data because the data were for all events in one or more years. The main concern might be the age of the detailed studies; in all three cases it is deemed unlikely that the basic scheduling of events changed substantially in the past 10 years.

The ratios for health clubs have not been modified from the second edition, which were primarily based on 16 studies conducted at that time, in a proprietary study, which is judged to be more reliable by NPA’s PCC then the data in PGM.

The ratios for residential units have been significantly changed. Previously, there were separate ratios for rental and owner-occupied residential units. The PGM does not find any significant variation between owned and rental, and less than 5 percent variation between low- and mid-rise residential. However, it may still be appropriate to use a lower driving ratio for rental when the census data indicate. The PGM finds that a ratio based on bedrooms is more statistically reliable than a ratio per dwelling unit, a conclusion which most parking consultants have long believed is quite rational. Therefore, the basis of the ratios has been changed to use the distribution of bedroom types (studio, one bedroom, two bedrooms, and three-plus bedrooms) with the overall ratio per bedroom calibrated to the findings of the PGM. Another change is that the time-of-day factors are different for General Urban/Suburban projects than for CBD and TOD projects, particularly on weekdays. In CBD/TOD projects, the cars that are owned by residents are more likely to be left parked at the complex in the daytime on weekdays, with the tenants using transit, biking, or walking for commuting to work. The accumulation of vehicles for all residential at midday has been lowered, which will significantly affect many shared parking studies if indeed the residential parking is part of the shared parking pool and not reserved for residents only.

Ratios and default values have also been added for senior housing, based primarily on a single study in one city, albeit with parking demand studied at multiple sites.

For hotels, the ratios have been significantly changed, first to provide employee parking ratios for each component (keys, restaurant, and meeting/convention space) rather than based solely on keys. Further, the meeting/convention space ratios are scaled continuously, rather than having big jumps at borders based on square feet of space per key. Default values are also discussed and recommended to reflect the significant impact that TNC use is having on overnight guest and other parking at many hotels. The ratios themselves, however, are based on the second edition. A significant impact on hotel parking demand from ride hailing is noted, particularly for business travelers on weekdays. At this time, it is deemed best to adjust from ratios without significant ride hailing, and thus from the second edition ratios (as modified herein) rather than lower the ratios to reflect typical ride hailing today.

This third edition of Shared Parking maintains the same four categories of offices and scale ranges for general office but changes the name of data processing offices to high-density offices. Although employee density has clearly increased in some newly leased office space today, little data exist that parking ratios have increased across the board. Indeed, a special sort of the PGM data by the ITE team indicates that parking ratios for general office space have declined since 2010, which NPA’s PCC believes is caused by work-related travel, telecommuting, and flexible hours. Chapter 4 has an extensive discussion of the issues of employee densification and its impact on parking ratios. To summarize, the data reviewed by NPA’s PCC for Shared Parking do not indicate that office worker density/presence and parking demand are increasing significantly when tabulated across multiple tenants of undoubtedly different lease rollovers in existing buildings. Some offices today are recognized as having higher worker densities. Therefore, the key recommendation for office parking demand is to determine the expected percentage of high-density office in a building or complex and apply the general office and high-density office ratios to that breakdown.

The medical office and bank ratios and default values have also been modified based on the PGM.

An entire chapter on regional variations in parking demand is included, as well as future projections based on potential mobility changes because of TNCs and AVs. Although those impacts are still difficult to predict both in terms of timeline and ultimate impact on parking, high disruption and low disruption forecasts of impact on parking demand nationally are provided with a timeline that is much slower than the oft-quoted 90 percent reduction in parking by 2030. The latter projection has largely been discredited as unrealistic, even in urban CBDs. While TNCs may launch true driverless service in selected cities by the early 2020s, there is increasing acceptance that they will be driverless only in areas that have been mapped in the cars’ programming and in good weather conditions. An autonomous vehicle that can operate anywhere, anytime, is at least a decade off and may be several decades off, according to automobile experts and even the TNCs themselves. Even then, a 90 percent reduction in parking is simply impossible to reach because of the demographics of urban/suburban/rural populations, much less the idea that 90 percent of Americans who could, will give up vehicle ownership and use TNCs and transit.

Therefore, and again, the third edition of Shared Parking is intended to facilitate a just enough, no regrets parking supply for mixed-use projects being developed in the foreseeable future.

NOTES

1. ULI–the Urban Land Institute, Shared Parking (Washington, DC: ULI–the Urban Land Institute, 1983).

2. What Is Smart Growth?, https://smartgrowth.org/what-is-smart-growth/, August 2018.

3. About Smart Growth, www.smartgrowth.org/about, October 2003.

4. R. Bose and F. Rood, 2019. The Nexus between Land Use and Fiscal Balance, Zoning Practice 1 (January 2019).

5. Placemaking, Wikipedia, August 2018, https://en.wikipedia.org/wiki/Placemaking.

6. ULI, Creative Placemaking, Building Healthy Places Initiative, August 2018, https://americas.uli.org/research/centers-initiatives/building-healthy-places-initiative/creative-placemaking/.

7. ITE, Parking Generation Manual, 5th ed. (Washington, DC: Institute of Transportation Engineers, 2019).

8. The Shared Parking Model uses 13 months, adding Late December as an additional month distinct from December: December = December 1–24; Late December = December 25–31.

CHAPTER 2

Methodology, Analysis, and Assumptions

This chapter presents recommendations for the methodology as well as recommended default values for certain assumptions to be used in a shared parking analysis.

METHODOLOGY

The shared parking methodology herein provides a systematic way to apply appropriate adjustments to parking ratios for each use in a mixed-use development or district. This methodology is summarized in figure 2-1.

Later in this chapter each step is reviewed in more detail, but first the importance of each of these steps must be outlined. Steps 1 and 9, which involve developing an understanding of the project before starting analysis and developing site design and parking management plans that will facilitate shared parking (after the recommended number of spaces is determined), are often neglected in many shared parking studies. The analysis may reliably project the peak accumulation of vehicles, but if the design and management of the parking system do not facilitate the sharing of spaces, parking may be inadequate. Although management practices can often be changed to improve the situation, a poorly designed site for shared parking often cannot be significantly improved, and more spaces may ultimately have to be added. Chapters 5 and 6 are devoted to this topic.

One of the key changes in the methodology from the first to the second edition of Shared Parking was the separation of parking ratios into visitor/customer, employee/resident, and reserved components. This delineation, which is retained in the third edition, facilitates application of different noncaptive and driving adjustments, since those characteristics may be distinctly different in certain locations and with certain combinations of land uses. Other analysts have termed this long-term and short-term demand. Technically speaking, however, some customers (such as hotel guests) park as long or longer than employees, and part-time employees often qualify as short-term parkers (by most definitions, those who stay less than three or four hours).

The modal splits to private automobile for customers and employees are likely to be somewhat different in areas with good public transportation. Employees of tenants in an office complex are more likely to use public transportation or to carpool than visitors to those same tenants. The time-of-day adjustments also show some differences, depending on whether the user is an employee or tenant. The employees, performers, and staff at a performing arts center will arrive several hours before a scheduled performance, and a small number of staff will be present during normal business hours to handle the daily activities of managing the facility.

Perhaps the most important reason to separate the employee and visitor parking ratios is to facilitate parking management for a mixed-use complex or activity district. For example, when downtown mixed-use projects are developed, it may be determined that the parking added for the project should accommodate only customer parking needs. A downtown area usually has multiple parking options for employees at various price points; adding significant spaces for employees in the core location may not be necessary or appropriate. This sharing of existing parking resources enables such projects to be more financially viable while maintaining