Accounting for Latent Travel Demand

Planners must anticipate how people would respond to new options, such as better walking, cycling and public transit services. This requires imagination.

3 minute read

May 19, 2013, 2:44 AM PDT

By Todd Litman


Once upon a time two competing shoe salesmen together visited an isolated community. After investigating the area one sent a telegram back to his office which read, “I’m returning tomorrow. Nobody here wears shoes!” while the other sent a telegram which read, “Send more product. Everybody here needs shoes!

This illustrates the concept of latent demand, which refers to new goods and services that people would choose if they were available. The first saleman couldn't imagine currently barefooted people wearing shoes, the second saw opportunity.

This is an important factor to consider in planning; our job often entails anticipating how people would respond to new options and incentives, which can be difficult because it requires imagining a world that is different from what currently exists.

A good example of this is a recent column by the Georgia Public Policy Foundation (GPPF) opposing complete streets on the grounds that they harm commuters. Their arguments assume that Georgia's high automobile mode share is unchangeable and desirable. They cannot image a more multi-modal transportation system.

Yet, there is good evidence of significant latent demand for walking, cycling and public transport. A detailed study, Infrastructure, Programs, And Policies To Increase Bicycling: An International Review, and the U.S. Federal Highway Admimistration’s  Report to the U.S. Congress on the Outcomes of the Nonmotorized Transportation Pilot Program, indicate that walking and cycling improvements often significantly increase use of these modes.

Serving this demand can benefit everybody. Walking, cycling and public transit play unique and important roles in an equitable and efficient transport system. In a typical community 20-40% of the population cannot or should not drive due to age, ability or income, and many trips are most efficiently made by alternative modes. It is unfair if non-drivers are not given a share of transportation infrastructure resources, and it is inefficient if parents are forced to drive children to local destinations due to inadequate pedestrian and cycling facilities, or if lower-income households are forced to purchase more vehicles than is affordable due to inadequate transport options.

The GPPF also claims that road diets are dangerous. This is untrue. Several recent studies indicate that complete streets and road diets tend to increase traffic safety. Research by the Highway Safety Research System concludes that road diets typically reduce overall crash rates 29%.

Complete streets policies can provide particularly large benefits in automobile-dependent communities were many roads lack sidewalks and crosswalks, and cycling is dangerous. A tragic example of this problem was the case of Raquel Nelson, who was found guilty of vehicular homicide because her 4-year-old son was struck by a van and killed while the family was crossing a busy Atlanta-area highway that lacked crosswalks. This is exactly the type of accident that complete streets policies can reduce.

Imagine a better world, a world in which roadway design better responds to demands for walking, cycling and public transit.

For More Information

AARP (2009), Planning Complete Streets for an Aging America, American Association for Retired Persons Public Policy Institute.

Heather Contrino and Nancy Mcguckin (2009), “Travel Demand in the Context of Growing Diversity: Considerations for Policy, Planning, and Forecasting,” TR News, Transportation Research Board (www.trb.org), September-October, pp. 4-9.

Eric Dumbaugh (2005), “Safe Streets, Livable Streets,”Journal of the American Planning Association, Vol. 71, No. 3, pp. 283-300. 

HSIS (2010), Evaluation of Lane Reduction “Road Diet” Measures on Crashes Summary Report Research, Development, and Technology, Highway Safety Information System.

Todd Litman (2010), Evaluating Non-Motorized Transport Benefits and Costs, Victoria Transport Policy Institute.

Todd Litman (2012), Evaluating Complete Streets: The Value of Designing Roads For Diverse Modes, Users and Activities, Victoria Transport Policy Institute.

PPS (2012), Rightsizing Streets, Project for Public Spaces (www.pps.org); at www.pps.org/reference/rightsizing.

Carol H. Tan (2011), “Going On A Road Diet: Lane Reduction Can Increase Safety For Pedestrians, Bicyclists, And Motorists While Improving The Quality Of Life In Downtowns Across The Country,”Public Roads, U.S. Federal Highway Administration.

WSDOT (2011), Washington’s Complete Streets and Main Street Highways: Case Study Resource, Community Planning and Development, Washington State Department of Transportation.


Todd Litman

Todd Litman is founder and executive director of the Victoria Transport Policy Institute, an independent research organization dedicated to developing innovative solutions to transport problems. His work helps to expand the range of impacts and options considered in transportation decision-making, improve evaluation methods, and make specialized technical concepts accessible to a larger audience. His research is used worldwide in transport planning and policy analysis.

Aerial view of homes on green hillsides in Daly City, California.

Depopulation Patterns Get Weird

A recent ranking of “declining” cities heavily features some of the most expensive cities in the country — including New York City and a half-dozen in the San Francisco Bay Area.

April 10, 2024 - California Planning & Development Report

Aerial view of Oakland, California with bay in background

California Exodus: Population Drops Below 39 Million

Never mind the 40 million that demographers predicted the Golden State would reach by 2018. The state's population dipped below 39 million to 38.965 million last July, according to Census data released in March, the lowest since 2015.

April 11, 2024 - Los Angeles Times

A view straight down LaSalle Street, lined by high-rise buildings with an El line running horizontally over the street.

Chicago to Turn High-Rise Offices into Housing

Four commercial buildings in the Chicago Loop have been approved for redevelopment into housing in a bid to revitalize the city’s downtown post-pandemic.

April 10, 2024 - Chicago Construction News

Young woman and man seated on subway car looking at phones.

Google Maps Introduces New Transit, EV Features

It will now be easier to find electric car charging stations and transit options.

6 hours ago - BGR

Ohio state capitol dome against dramatic lightly cloudy sky.

Ohio Lawmakers Propose Incentivizing Housing Production

A proposed bill would take a carrot approach to stimulating housing production through a grant program that would reward cities that implement pro-housing policies.

7 hours ago - Daytona Daily News

Aerial view of Interstate 290 or Eisenhower Expressway in Chicago, Illinois.

Chicago Awarded $2M Reconnecting Communities Grant

Community advocates say the city’s plan may not do enough to reverse the negative impacts of a major expressway.

April 19 - Streetsblog Chicago

News from HUD User

HUD's Office of Policy Development and Research

Call for Speakers

Mpact Transit + Community

New Updates on PD&R Edge

HUD's Office of Policy Development and Research

Write for Planetizen

Urban Design for Planners 1: Software Tools

This six-course series explores essential urban design concepts using open source software and equips planners with the tools they need to participate fully in the urban design process.

Planning for Universal Design

Learn the tools for implementing Universal Design in planning regulations.