Parking Generation Update: The Numbers - Institute of ...

Parking Generation Update: The Numbers
Ransford S. McCourt, PE, PTOE
Principal, DKS Associates
The Institute of Transportation Engineers (ITE) Transportation Planning Council decided
to actively pursue updating the Parking Generation Informational Report in 1999. In the
following three years, the historic parking demand survey records were converted to
current spreadsheets formats to preserve the data for future use and nearly four times
more data was obtained through various sources to enrich the available information on
parking demand. The third edition of the Parking Generation Informational Report
represents a substantial change from the second edition published in 1987, providing the
profession a new tool to better understand the relationship between land use and parking
demand.
Since the decision to update Parking Generation, ITE has formed the Parking Council
that will become responsible for future updates to the informational report and managing
the data acquisition. It is anticipated that publication of the updated Parking Generation
will reinvigorate interest in parking demand stimulating significant new data for further
updates to the informational report.
Several new user features have been added to summarize data and statistical information
of the surveys submitted. In the first two editions of Parking Generation, emphasis was
placed on averaging the maximum observed parking demand primarily from isolated,
suburban sites to obtain parking demand ratios. This update begins a process of
segregating parking data records for future analysis and research into various factors that
may affect parking demand. Parking data is linked to the hour of observation to provide
a temporal understanding of parking demand and the peak hour of parking demand.
Additionally, this update separates out the influences of area type on parking demand,
including (where data is available) information about sites that have priced parking.
This update only begins to explore the variations in parking demand based upon these
other factors. Much of
data currently available is
from unpriced, suburban
sites with isolated single
land uses. As future
studies are submitted, they
will provide a basis to
assess factors such as type
of area, pricing, transit
availability/quality,
transportation demand
management plans, mixing
of land uses, pedestrian
friendly design, land use
density, trip

chaining/multi-stop trip activity, employee/visitor parking, long term/short term parking
and other issues in more detail. Where information of this type was available, it has been
reported; however, at this time the extent of data in this area is limited.
More parking data is needed to understand the complex nature of parking demand. This
informational report does not provide authoritative findings, recommendations or
standards on parking demand. It should be understood that assemblage of data and
production of this report are a fully-volunteer effort and not the result of a financed
research effort. As such, the report contains useful parking demand data – ranges of
information and statistics are provided only as an informational guide to planners and
designers regarding parking demand.
There is a tendency to focus on a single number (such as the average) to form the basis
for estimating parking demand. Care should be utilized in applying the information
presented in this informational report to estimate parking demand, reflecting upon ranges
of demand, statistical quality and quantity. Information (where available) regarding other
factors (such as transportation demand management, area type, pricing and several
others) is also provided.
Because of the cost of providing parking, it would be appropriate to seek guidance from
parking professionals with experience in understanding the many variables that can affect
parking demand rather than simply utilizing a single number from this informational
report.
Objective
To build a comprehensive understanding of parking
demand characteristics of various land uses by
providing a process to easily expand the parking
demand data set, continually updating information
and reaching as many potential users, researchers
and professionals as possible.
Organization of Report
The Parking Generation Informational Report
provides the following sections:
• Use of the Parking Generation Report
This section outlines how to use information
in this report answering basic questions
such as “What is an Informational Report”
• Data Analysis
This section outlines the statistics that have been utilized and the basic guidelines
for defining the quality of data as well as the quantity of data

• Definitions
This section provides a glossary of terms utilized in this report, particularly
related to independent variables and statistics.
• Format of Data Provided for Each Land Use
This two page summary outlines how the data for each land use code is organized
and where to find key information.
• Parking Data by Land Use Code
This is the core data for Parking Generation organized by ITE Land Use Code
(over 100 land uses are described).
• Summary of Parking Data (Appendix A)
These tables provide a quick reference guide to the parking data, collapsing
hundreds of pages of data into a few summary sheets.
• Parking Data Sources (Appendix B)
This section provides the sources of each parking survey utilized in this report,
indicating the name of the data provider, location (city) of their survey and the
month/year of the survey.
• Mixed-Use Parking Data (Appendix C)
This section summarizes a limited number of surveys submitted to ITE for mixedland
use sites. While little statistical data is provided, these surveys provide
analysts with parking demand case studies to compare shared parking
calculations with reality.
• Data Collection Techniques (Appendix D)
This section provides
information on how to collect
parking demand information,
how parking data contained in
this report was obtained and
resources such as the parking
demand data collection form.
It also outlines the Parking
Generation Committee’s
recommended areas for
additional parking demand
surveys and suggests some
approaches that local ITE
Chapters, Sections or Districts
may employ to increase the
quantity and quality of data.

Update Process
The current process to update Parking Generation began in Las Vegas in 1999 at the ITE
Annual Meeting. Over the next 18 months, all of the historical data records from ITE
were entered into spreadsheets as a data base and other data sources were contacted.
Following Parking Generation Committee meetings in Nashville (00), Monterey (01),
Chicago (01) and Philadelphia (02) – open houses were conducted, presentations (nearly
a dozen) were made to professionals and substantial emailing of ITE members was
undertaken. At these meetings, presentations and open houses – issues such as the
format, preliminary data, type of information, statistics, means to obtain data and text
were reviewed.
The ITE web site has been used to announce the update activities in 2001, opening a
communication link with the profession. Newsletters (Traffic Council, Transportation
Planning Council, Parking Council, WesternITE, section news) were used to request
volunteer support and data. Searches on the internet were conducted to determine where
additional existing parking demand data may exist; followed by individual contact.
Beyond this, numerous ITE members and parking associations were notified via
email/mail of the update process and were requested to contribute any parking data they
might have available. Comments provided by member (including member surveys)
provided insights into the user features that professionals desired most and allowed the
Parking Generation committee review how the information report would be organized for
this update. All of these efforts resulted in substantial new data being added to Parking
Generation.
Key Features of the Update
More Data: Surveys conducted of ITE members in
the early 1990’s indicated that more data was the most
important need for Parking Generation. The number
of surveys in Parking Generation has been increased
from about 1,000 studies to nearly 4,000 studies.
These studies represent nearly 11,000 hours of parking
observations. About 40 percent of the data is from
surveys conducted after 1990.
1990s
26%
2000s
13% Pre-1985
26%
Use of Formulas and Accuracy. The member
surveys indicated a concern about the use of formulas
for parking demand when limited data existed. The update establishes statistical quantity
and quality guidelines for the use of regression formulas. Numbers are generally rounded
off to a single decimal point. Additional statistical data are included such as 95 th
confidence interval, coefficient of variation and 85 th percentile as tools for analysts.
1985-1989
35%

2000
LAND USE 710: Office Buildings
Maximum Observed Parking Demand Plot
Suburban Sites
1800
1600
Number of Vehicles
1400
1200
1000
800
600
400
200
0
- 100,000 200,000 300,000 400,000 500,000 600,000 700,000
Building Square Footage
y = 0.0027x
R 2 = 0.90
More Land Uses. Another response to member surveys was including more land use
categories. Nearly 50 new land uses have been added to Parking Generation including
those noted below:
LRT Station with Parking Convention Center US Post Office
Mini-Warehouse Ice Skating Rink Courthouse/Corrections
Single-Family Housing Snow Skiing Area Business Park
Rented Townhouse Casino/Video Lottery Establishment Building Materials/Lumber Store
Elderly Housing - Attached Athletic Club Coffee Store
Elderly Housing - Congregate Elementary School
Discount Market
Middle School
Assisted Living Private School Discount Store
All Suites Hotel Junior/Community College Home Improvement Superstore
Business Hotel Day Care Center Electronics Superstore
Golf Course Museum Sporting Goods Superstore
Billiard Hall Library Apparel Store
Adult Cabaret Corporate Headquarters Building Pharmacy without Drive-Through
Music Hall Single Tennant Office Building Pharmacy with Drive-Through
Live Theater Medical/Dental Office Building Video Rental Store
Hour of Day Parking Variation. The parking demand data is now organized by hour of
observation allowing for analysis of parking variation over the course of the day.
Information is provided in some cases by day of week and month of year to assist
understanding of when peak parking demand occurs.

Heath Club Hourly Variation
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
7:00 AM
8
9
10
11
12 Noon
1:00 PM
2
3
4
5
6
7
8
9
Beyond Suburban Sites. This update provides, for limited land uses where data exists,
information about variation in parking demand for different area types (suburban,
suburban center, central business district, central city-not downtown, rural) and pricing of
parking. While more data is needed in this area, this begins a process for encouraging
future data collection.
Mixed-use Sites: To encourage understanding of sites where multiple land uses are
provided, mixed-use site case studies are now documented. While only seven sites were
available, greater data collection in the future will provide a case study resource similar
to pass-by trip in Trip Generation.
Shared Parking. Provision of the hourly variation in parking demand is the major
difference between this update and the prior versions of Parking Generation. Tables are
provided that compare the peak hour of parking demand observation to the other hours of
the day on weekdays and weekends (where data are available). The Urban Land Institute
is planning an update to their Shared Parking report building from the Parking
Generation findings.
Land Use Differentiation: For three land use groups (fast food restaurants, athletic
clubs and senior housing) more detailed differentiation between the land use types was
developed. For example, for fast food, specific data for hamburger, taco, pizza stores
was provided. Senior housing has been divided into land use categories that are standard
for that industry. Additionally, athletic clubs have been divided into the various types
commonly found – member athletic clubs, fitness/health clubs, racquet clubs, recreational
centers and tennis courts.

Call for Data
Additional parking demand data is needed for numerous land use categories. An easy to
use Excel spreadsheet for parking data is available to be downloaded from the ITE web
site (www.ite.org/surveys/parkingoccupancy/parking_basicform.xls). The Parking
Generation Update Committee identified the following priority areas for data collection:
• Grocery Stores (examples include small - 7/11; medium - IGA; and large-Albertson's,
Safeway)
• Elderly Housing (senior housing - attached or detached, nursing homes, assisted
living, congregate care, continuing care retirement communities)
• Large Cinemas (16 or more screens)
• Big Box Retail (examples include Costco,Wal-Mart, Home Depot, Lowe’s, Target,
Toys-r-us, K-Mart, Sports Authority, Borders, Staples,....)
• Restaurants (quality restaurants to high turnover to fast food)
• Civic Facilities (library, city hall, recreation centers, fire/police stations)
• Warehouses
Conclusion
The update to Parking Generation provides a powerful new tool to better understand
parking demand. On the other hand, it provides information that can easily be
misinterpreted without good professional judgment. Having reviewed every piece of
information summarized in this report, if users do not reflect on the unique characteristics
and factors that can affect parking demand site by site or the need for additional data –
this report will not help them. Many times the complexity of parking demand requires
the understanding of professionals experienced with analyzing parking characteristics.
This update provides a starting point to better understanding of the characteristics that
affect parking demand (area type, transit services, demand management strategies,
pricing, shared parking) and encourages more surveys to verify data in this report.
Ransford S. McCourt, PE, PTOE is a principal of DKS Associates in Portland, Oregon.
He manages the DKS offices in Portland, Seattle, Washington and Phoenix, Arizona. He
chairs the ITE Parking Generation Update Committee and is the Vice Chair of the ITE
Parking Council. In 2003-2004 he will be President of ITE District 6.