The Dimensions of Parking

The Dimensions of Parking

by Urban Land Institute

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Analyzing the requirements of both free and pay parking lots, this reference reveals the best practices for planning, designing, financing, building, and operating an efficient facility. Parking studies and expert practitioners provide insights and solid how-to information on a bevy of topics, including zoning requirements, automated structures, spacing


Analyzing the requirements of both free and pay parking lots, this reference reveals the best practices for planning, designing, financing, building, and operating an efficient facility. Parking studies and expert practitioners provide insights and solid how-to information on a bevy of topics, including zoning requirements, automated structures, spacing geometrics, drainage and ventilation systems, and security considerations.

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The Dimensions of Parking

By Urban Land Institute

Urban Land Institute

Copyright © 2010 Urban Land Institute
All rights reserved.
ISBN: 978-0-87420-238-0





ADEQUATE, CONVENIENT, AND AFFORDABLE PARKING is a concern for nearly everyone who uses an automobile — or is affected by the use of automobiles. First, automobile parking is essential to most land uses. Second, parking affects property values and influences the economic return on public and private sector investments. Finally, on a broad scale, decisions about parking influence travel behavior, including choice of travel mode, and land use and development patterns.

The development, construction, operation, and maintenance of parking facilities represent a significant expense and usually call for both public and private sector involvement. Public involvement can range from the typical permitting and regulatory actions to full responsibility for developing and operating parking facilities. Most parking, however, is developed and operated by the private sector.

Regardless of how responsibilities are allocated, the intricacies of parking warrant careful analysis and coordinated decision making. As a result, parking consultants are now typically involved in all aspects of the development and operation of parking facilities. The parking consultant's role is to provide technical assistance to those who are in decision-making positions: public and private sector managers; elected officials and their staff; investors; and real estate developers. Parking consultants are familiar with the parking characteristics associated with most land uses, and understand that proper data collection, careful analysis of site-specific circumstances, and experienced judgment are crucial to the successful development of parking facilities.

Some parking consultants offer highly specialized services; others provide comprehensive services, including the following:

* planning and site studies;

* traffic studies and engineering reports;

* design;

* construction management;

* financial analysis;

* operations consulting; and

* recommendations for maintenance and repair.

Whether the problem is how to meet current or future needs, how to improve operations, or how to evaluate the need for maintenance and repair, the first step is often a parking study. There are as many types of parking studies as there are parking problems to be solved. In general, however, the consultant undertaking the study evaluates a parking problem and its causes, analyzes alternative solutions, and develops recommendations on the basis of site-specific evidence. The consultant may also identify opportunities for coordinated actions, detail the probable ramifications of implementing those actions, and provide an estimate of financial and other costs. No parking study should be more voluminous than necessary, and it should communicate in a way that is easily understood by nonspecialists; ideally, the client should be able to use the data to arrive at the same conclusions as the professionals who performed the study.

Typically, a parking study includes three components: a parking supply/demand analysis; a site alternatives analysis; and a financial analysis. Some studies include only one of these three components; others include additional components, such as an analysis of traffic impacts or of parking management and operations. The following list describes some of the elements that may be included in parking studies.

* Parking supply/demand analysis. An evaluation of the current and future amount of parking space in relation to demand; identifies shortages or surpluses.

* Market study. A projection of the number of users who may be captured by a facility on a particular site, given demand, competition, and prevailing parking rates.

* Shared-parking analysis. A projection of parking demand in mixed-use areas that takes into account (1) variations in demand by season, day of the week, and time of day, and (2) the relationship between parking needs and planned land uses.

* Alternatives analysis. An evaluation of the alternatives that can be used to increase parking capacity and perhaps reduce parking demand; typically undertaken where there are documented parking shortages.

* Schematic design. A functional design for a proposed parking facility, developed to a sufficient level of detail to obtain consensus among interested parties. (Normally, design documents are not prepared until the first phase of a design contract, but they may be necessary during the study phase to provide the background information needed to obtain consensus and proceed with design and funding.)

* Traffic impact analysis (TIA). The application of standard methods of traffic engineering analysis, with the goal of identifying current and/or future traffic conditions and recommending improvements. Although the TIA generally focuses on determining the effect of a proposed parking facility on traffic conditions, it sometimes addresses existing traffic problems that should be considered simultaneously with parking needs.

* Financial analysis. A projection of the operating expenses, revenues, and sometimes the debt service associated with a proposed new facility or with the expansion of an existing facility; includes an assessment of the owner's ability to fund the improvements through parking income. The financial analysis may include some or all of the following elements:

* estimates of development costs;

* estimates of use and rates;

* projections of revenue and operating expenses;

* financing costs, including interest rate and terms;

* analysis of the ability of a parking facility to service debt on its own; and

* analysis of the viability of adding a new facility to an existing system.

* Financing method analysis. A study of available financing methods and their legal ramifications: evaluates the interest rate and terms; insurance; debt reserves; and other requirements. Financing options may include public/private partnerships; federal, state, or local financing programs; private ownership and financing; and nontraditional funding sources.

* Parking management study. An identification and analysis of parking problems that can be corrected through changes in policy, management, or operating strategies.

* Organizational and administrative review. A detailed study of the administration and operation of the parking system as a whole; considers issues such as use and allocation of resources, staffing needs, assignment of responsibility, and general organization. The review is often needed to establish an authority or agency that will run an entire parking system.

* Parking revenue controls and operations study. A review of current revenue collection systems and other policies and procedures to ensure that revenue is maximized and that theft, fraud, and evasion are minimized.

* Equipment acquisition analysis. A review of current operations for the purpose of determining the appropriate type and number of access and egress lanes and recommending control equipment. The study phase usually includes cost estimates and an outline of specifications; detailed construction documents are developed later.

* Parking facility evaluation. An evaluation of the extent of deterioration in a parking structure floor and frame; includes repair and cost estimates, and may include recommendations designed to maximize revenues and mitigate theft, fraud, and evasion. Construction documents for repairs are not part of a parking study.





FOR MANY LAND USES, THE AMOUNT OF PAVED PARKING area is as great as, or even greater than, the occupied area of the buildings being served. For example, an office building may have a 1:1 ratio of parking area to leasable space; a shopping center may have approximately 1.5 square feet (0.14 square meters) of paved parking area for each square foot (0.09 square meters) of gross leasable area. The number of parking spaces provided for a site, complex, or district is thus a key determinant of its character. In the words of former Disney CEO Michael Eisner, "Form follows parking."

Because parking is so crucial to the success of the development it serves — whether that development is commercial or institutional — developers and property owners want to be sure that parking is adequate. Local governments, for their part, want property owners to provide enough off-street parking to prevent tenant or visitor parking from overflowing to public streets or adjacent private property. Nevertheless, it is not in the interest of either the private sector or the public sector to require an excessive amount of parking. Because parking is a necessary component of development, the land area and/or resources devoted to parking may constrain the amount of development that a given site can support. Moreover, excessive parking requirements often lower the density of development; reduce land values; reduce the economic viability of public transportation; undermine the walkability of the site, complex, or neighborhood; and damage the natural environment.

Parking is a key component of transportation demand management — a set of strategies that are designed to make more efficient use of transportation resources. When parking is oversupplied, it is likely to be undervalued. As Donald Shoup notes in The High Cost of Free Parking, drivers park free for 99 percent of all automobile trips, which means that the cost of parking is almost never a factor in transportation decisions. Shoup also notes that "planning education provides no instruction on how practicing planners should set parking requirements and textbooks offer no help."

In recent years, three separate but related planning approaches have focused attention on the negative impacts of the "more is better" philosophy of parking: smart growth, transit-oriented development (TOD), and new urbanism. All three approaches strive to use land more efficiently, contribute to the availability of affordable housing, reduce dependence on automobile travel, and create more livable communities. All three also rely heavily on the same things: "mixed use, higher density, buildings at the sidewalk, less private and more public open space, smaller blocks, narrow streets with wider sidewalks, street trees and lighting, lower parking ratios, shared parking, parking behind buildings, and on-street parallel parking." Carefully crafted parking requirements support the values that underlie smart growth, TOD, and new urbanism.

This chapter describes the basics of analyzing parking demand: the first major section describes the principal estimation methods; the second discusses issues in demand estimation; the third examines the use of recommended ratios; and the fourth describes how to refine demand estimates. Estimations of parking demand are used for multiple purposes: by developers, tenants, and lenders who wish to ensure that adequate parking will be provided; by local officials, to determine parking requirements for zoning ordinances; by developers who wish to obtain reductions in the amount of parking required by local ordinances; and by financial planners, who must project usage levels for facilities where paid parking is contemplated. Chapter 3, "Shared Parking," discusses demand estimation for shared-parking situations, and Chapter 4, "Zoning Requirements," addresses the development of parking requirements for zoning ordinances.


Parking demand is defined as the number of spaces that should be provided to serve a particular land use, given factors such as the price of parking and the availability of alternative travel modes. There are two basic approaches to estimating parking demand. The first approach begins with recommended parking ratios, which are then adjusted to reflect local characteristics. The recommended ratios are based on industry standards — which, in turn, are typically based on free parking in locations where virtually 100 percent of the arrivals are by private automobile.

The second technique, which bases the estimate of parking needs on a forecast of person-trips or vehicle-trips, or on the number of people expected to be present at peak hours, is often used for event facilities, such as performing-arts centers, arenas, or stadiums. (It is important to note, however, that when parking demand is estimated on the basis of person-trips or vehicle-trips, it is generally converted to a ratio of spaces per unit of land use, so that the resulting ratio can be compared to industry standards and to zoning requirements.) Parking demand for a particular event can be estimated on the basis of three pieces of information: the number of seats, the modal split (the percentage of attendees who arrive by private auto), and the number of persons per car. Employee parking needs can be estimated similarly, on the basis of the number of employees on duty, the modal split, and persons per car.

Both approaches — those based on parking ratios and those based on estimated person-trips, vehicle-trips, or seating capacity — yield fairly accurate forecasts of parking demand, as long as the proper amount of research is conducted and strong consideration is given to local conditions. Industry standards — whether for parking ratios, person-trips, or vehicle-trips — cannot be applied without attention to local characteristics.

The key is to gather as much information about the site as the client can provide, to compare that information to standards established by industry organizations, and to adjust for differences in various factors, including density, availability of public transportation, local policies, the price of parking, and economic vitality. It is important to note, however, that budgetary limitations may prohibit extensive field surveys and analytical work, restricting analysts' ability to collect detailed data.


The next five sections consider a number of issues and practices with which parking analysts and their clients must be familiar: (1) the units used to express parking ratios; (2) the impact of the size of the land use on parking ratios; (3) the delineation of the study area for parking-demand analysis; (4) the determination of design day and design hour; and (5) the impact of effective supply.


Parking requirements are generally stated as a ratio of spaces per unit; the particular unit varies by land use, but is usually square footage. Other units that may be used are per dwelling unit, bed, hotel room, seat, or person. Ideally, the unit will be something that can be calculated during project planning. Thus, demand ratios based on the number of employees, which often varies over time, should be avoided. However, parking requirements for certain land uses, especially institutions such as hospitals and schools, are so variable that per employee, per student, or per patient may be the only reasonable units. In some cases, particularly for spaces such as auditoriums, the maximum legal capacity can serve as the basis for parking requirements.

In the past, parking ratios tended to be stated as one space for X number of square feet. But most industry groups now prefer to state the ratio as X number of spaces per 1,000 square feet (or Y spaces per 100 square meters), because it is easier for the average person to multiply than to divide. When the number associated with the unit is consistent, the magnitude of the requirements — and the differences between them — are easier to grasp. For example, 1 space per 200 square feet (19 square meters) and 1 space per 250 square feet (23 square meters) are equivalent to 5 spaces and 4 spaces per 1,000 square feet (5.4 and 4.3 spaces per 100 square meters), respectively.

When ratios are based on square footage, how the square footage is calculated is an important consideration. Because there is wide variation among both industry standards and zoning ordinances on this issue, the following modifiers are often added for clarity: gross floor area (GFA), gross leasable area (GLA), net floor area (NFA), and net rentable area (NRA).

While older ordinances and references tended to use NFA, most industry standards today, including those of the Urban Land Institute (ULI) and the Institute of Transportation Engineers (ITE) use GFA — or, for multi-tenant buildings, GLA.The adjustment of square footage to reflect leasable or rentable area has become particularly important because of the trend toward large developments with multiple tenants: merely enclosing the space connecting the tenant spaces does not add to parking demand. Because the difference between GLA and GFA is negligible in smaller buildings, many standards use GFA for single-tenant buildings but GLA for multitenant buildings.


Higher parking ratios are often appropriate for small concentrations of a specific land use than for larger buildings in the same land use category. The reasoning is simply a matter of probability: among 50 small office buildings, a number will have demand that is high enough to justify a 3.8/1,000 parking ratio. But if the tenants of those 50 buildings moved into one large building, some of the tenants will regularly have an unusually high concentration of employees and/or visitors, while others will have few visitors, or will have employees who are often "on the road"; a 2.8/1,000 supply will therefore be sufficient. Different ratios for the same use are therefore entirely appropriate.

It is important to note that parking demand does not always decline as the quantity of a land use increases. For example, it is well established that parking ratios for shopping centers increase as the size of the center increases. This pattern is caused by the fact that the larger the center, the more likely patrons are to visit multiple tenants — which lengthens their stays and increases demand.


Excerpted from The Dimensions of Parking by Urban Land Institute. Copyright © 2010 Urban Land Institute. Excerpted by permission of Urban Land Institute.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

Meet the Author

Urban Land Institute is a nonprofit research and education organization devoted to the responsible use of land and the creation and maintenance of thriving communities worldwide. National Parking Association is an international network of more than 1,200 companies representing thousands of parking-industry professionals.

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