Accessibility-Based Planning

Todd Litman's picture

Should society encourage parents to drive children to school rather than walk or bicycle? Should our transportation policies favor driving over walking, cycling, ridesharing, public transit and telecommuting? Probably not. There is no logical reason to favor automobile travel over other forms of accessibility, and there are lots of good reasons to favor efficient modes, so for example, schools spend at least as much to accommodate a walking or cycling trip as an automobile trip, and transportation agencies and employers spend at least as much to improve ridesharing and public transit commuting as automobile commuting. Yet, current transport policies and planning practices tend to be biased in ways that favor automobile travel over other transport modes, and mobility over other forms of accessibility.

I spend a lot of time trying to educate planners about these issues. For example, I point out that the current way we evaluate transport system performance, using roadway level-of-service ratings or average traffic speeds, only reflects automobile travel conditions and therefore favors automobile-oriented improvements, such as expanding roadways and parking facilities, even if this degrades access by other modes and stimulates sprawl. Many people (both transportation professioals and the general public) understand this concept: they realize that accessibility is a multi-facetted function affected by a variety factors: the ease of driving and parking, but also the ease of walking and cycling, the quality of public transit service, land use patterns (and therefore the distribution of destinations), the costs of different travel options, the ease of obtaining information about access options, and even the quality of telecommunications and delivery services.  

But some people don't get it.

For example, Professor David Hartgen's latest report, Gridlock and Growth: The Effect of Traffic Congestion on Regional Economic Performance, published by the Reason Foundation, is a case study in automobile-oriented analysis. The report assumes that "transportation" means driving, automobile traffic congestion is the primary transportation problem facing society, highway expansion is the only way to reduce congestion, and highway expansion consequences are entirely positive. These assumptions represent an older transportation planning paradigm and are no longer accepted among most planners.  

Transportation planning is increasingly multi-modal. Most transport models consider the quality of travel by automobile, HOV and public transit, and sometimes even cycling and walking. Multi-modal planning expands the range of solutions that can be considered in transport planning. For example, planners can compare the benefits of highway widening, HOV or bus lanes, rail transit improvements, and pricing reforms, so communities can choose the most cost effective and beneficial in a particular situation. 

Transportation professionals now recognize that other problems besides congestion are also significant and must be considered in transport policy analysis and planning, including road and parking facility costs, consumer costs, accident risk, energy dependency, pollution emissions, land use impacts, mobility for non-drivers, and public fitness and health objectives. Planners increasingly apply more comprehensive analysis, so communities can identify the most optimal solution overall, and avoid solutions to one problem that exacerbate other problems facing society, such as highway widening which increases downstream congestion, road and parking facility costs, consumer costs, accidents, energy consumption, pollution emissions and habitat loss due to induced vehicle travel and sprawl. 

Transportation professionals also consider a wider range of transportation system improvement options, including various highway operation and demand management strategies such as improvements to alternative modes, pricing reforms, more accessible land use development, and development of mobility substitutes such as telecommunications and delivery services that reduce the need for physical travel.

Hartgen's methodology is flawed. It calculates congestion costs compared with free flow traffic conditions, as if that were optimal. Yet, transportation professionals increasingly recognize that, unless roads are efficiently priced (peak period road tolls to reduce traffic volumes to optimal levels) congestion is unavoidable and highway expansion is economically inefficient. 

The report assumes there is a direct connection between highway expansion, congestion reduction and economic development. This assumption is outdated. Although highway expansion may have provided significant economic returns during the 1950s through the 1970s, when the Interstate highway system was first developed, the economic return has declined, since the most economically beneficial links have already been completed. If highway expansion provided significant economic development benefits, cities with the most highways per capita (Detroit, Kansas City and Memphis are current leaders) would have the least congestion and must successful economies. The results are actually the opposite: the most congested cities also tend to be most economically productive. Current research indicates that, without efficient pricing, urban traffic congestion tends to maintain equilibrium: it gets bad enough to discourage additional peak-period automobile travel, and travelers learn to take it into account when deciding where to locate and how to perform activities. For example, if high quality alternatives are available commutes will shift mode, and truckers will shift travel time to avoid traffic congestion. As a result, unpriced urban highway expansion provides relatively modest economic benefits, while improving public transit service quality is often a more cost effective congestion reduction strategy.  

The report only considers highway solutions and favor sprawl development. More objective analysis considers a wider range of solutions and attempts to identify the best solution for each situation, taking into account all options and impacts. In some locations that may be highway expansion but in others it may involve commute trip reduction programs, transit service improvements, road pricing, or more land use mix so people don't need to travel as far for errands and commuting.

Note, this is not the first of Hartgen's reports that I consider faulty and biased. You might want to review my report, A Good Example of Bad Transportation Performance Evaluation. 

For information see:  

Joe Cortright (2007), Portlands Green Dividend, CEOs for Cities (; at 

Todd Litman (2006), Smart Congestion Reductions: Reevaluating The Role Of Highway Expansion For Improving Urban Transportation, Victoria Transport Policy Institute (; at

Todd Litman (2009), Smart Transportation Economic Stimulation, VTPI (; at 

RAND (2008), Moving Los Angeles: Short-Term Transportation Policy Options for Improving Transportation, Rand Corporation (; at 

SACTRA (1999), Transport Investment, Transport Intensity and Economic Growth, Standing Advisory Committee on Trunk Road Assessment, Dept. of Environment, Transport and Regions (; summary report at 

Todd Litman is the executive director of the Victoria Transport Policy Institute.


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