The Results Are In: Residential TODs Produce 50% Fewer Car Trips

You drank the Kool-Aid; you know that if you link transit and land use to create transit-oriented development (TOD) the result is fewer car trips and a host of benefits. From Portland to Miami, Boston to Los Angeles, a record number of TODs are being built in the US. Yet most bankers, developers and regulators are drinking from a different cup. As a result the majority of new development adjacent to transit stops in America has been built in a manner oblivious to the fact that a rail stop is nearby.

6 minute read

October 29, 2007, 3:32 PM PDT

By G.B. Arrington


You drank the Kool-Aid; you know that if you link transit and land use to create transit-oriented development (TOD) the result is fewer car trips and a host of benefits. From Portland to Miami, Boston to Los Angeles, a record number of TODs are being built in the US. Yet most bankers, developers and regulators are drinking from a different cup. As a result the majority of new development adjacent to transit stops in America has been built in a manner oblivious to the fact that a rail stop is nearby. Therefore many of the hoped for benefits (less time stuck in traffic and lower housing costs to name two) are not being realized from a public investment of nearly $75 billion dollars in rail transit over the past 11 years.

New Research

New research recently completed for the Transit Cooperative Research Program provides the ammunition to build TODs that take the benefits of transit into account. The study completed by PB PlaceMaking, Dr Robert Cervero, The Urban Land Institute and the Center for Transit Oriented Development looked at how automobile use of residential TODs compared to conventional development.

Our research looks at the actual transportation performance of 17 built TOD projects. This was done by counting the passage of motorized vehicles using pneumatic tubes stretched across the driveways of TOD housing projects of varying sizes in four urbanized areas of the country: Philadelphia/N.E. New Jersey; Portland, Oregon; metropolitan Washington D.C.; and the East Bay of the San Francisco Bay Area.

Suburban Bias

One motivation for this research was to provide original and reliable data to help seed new professional guidance for building TODs. In part that means an update of the Institute of Transportation Engineers (ITE) trip generation and parking generation rates, from which local traffic and parking impacts are typically derived and impact fees are set.

Some analysts have identified a serious "suburban bias" in the current ITE rates. Most of the empirical data used to set generation rates are drawn from suburban areas with free and plentiful parking and low-density single land uses. Moreover, since ITE's auto trip reduction factors, to reflect internal trip capture, are based on only a few mixed-use projects in Florida; there has been little or no observation of actual TODs. The end result is that auto trip generation is likely to be overstated for TODs. This can mean that TOD developers end up paying higher impact fees, proffers and exactions than they should since such charges are usually tied to ITE trip rates.

TODs Produce 50% Fewer Trips

In fact, the results of this research clearly show TOD-housing produces fewer automobile trips in the four urbanized areas. The research confirms the ITE trip generation and parking generation rates over estimate automobile trips for TOD housing.

The ITE manual presents "weighted averages" of trip generation that this study showed to be flawed for TODs. The weighted average vehicle trip rates for this study were computed for all 17 projects combined for weekday, AM peak, and PM peak. Over a typical weekday period, the 17 surveyed TOD-housing projects averaged 44% fewer vehicle trips than that estimated by the ITE manual (3.754 versus 6.715 daily trips per unit). The weighted average differentials were even larger during peak periods – 49% lower rates during the A.M. peak and 48% lower rates during the P.M. peak.

Peak hour impact fees and traffic impact studies based on the ITE manual could be overstating the congestion-inducing effects of TOD-housing by as much as 50%. One result may also be unnecessary impact mitigation and roadway improvements. This means that policy makers and planners can "afford" to give TODs as much as 50% lower fees than traditional developments with no adverse effects on other areas of government budgets caused by traffic impacts.

New Standards Needed to Reflect Reality

Existing suburban standards assume virtually everyone drives. It should now be indisputable: TODs perform differently than conventional development. New parking and trip generation rates are necessary to reflect reality. Implementing the findings of this research will allow communities across America to capture the benefits of TOD and reap additional benefits from the substantial investment in transit.

New standards could result in wholesale changes in how we address the cost, impact and feasibility of residential development near transit. The implications of new standards are varied:

  • Local officials and neighborhoods may be more apt to support increases in residential densities near transit if they are shown proof significantly fewer trips result from TODs than in conventional development.
  • Developers would likely pay lower fees and extractions by as much as 50% to reflect the actual performance of residential TODs. Those savings can be passed on to consumers in the form of lower housing costs.
  • Parking availability and cost has a major impact on transit use. Transit agencies should plan for increased ridership from lower parking ratios for residential TODs.
  • Housing affordability is a crisis facing the nation. More affordable TOD housing should be available to the public because of lower development costs and the need for less expensive parking.
  • More compact environmentally sustainable development can result from less land being consumed for parking. U.S. EPA estimates each on-site parking space in infill locations can reduce the number of new housing units or other uses by 25 percent or more.

Implementing these findings should help result in better planned communities, less time stuck in traffic and more affordable housing. Let's get going.

Appendix: Snapshot from the study

All 17 projects studies were within an easy walk of high quality transit with a mix of modes – heavy rail, commuter rail and light rail. Projects ranged in size from 90 to 854 units. The primary use was residential though 6 of the 17 sites had incidental retail uses on the first floor.

Washington, D.C. - 59.9% below ITE A.M. peak rate The biggest effects were found in the Washington, D.C. metropolitan area. Among the five mid-to-high rise apartment projects near Metrorail stations outside the District of Columbia, vehicle trip generation rates were more than 60% below that predicted by the ITE manual.

Portland, OR – 49.63% below ITE A.M. peak rate After the Washington area, TOD-housing in the Portland area tended to have the lowest weekday trip generation rates – on average, around 40% below that predicted by the ITE manual. The Portland projects which performed best were those on the fringes of the City Center. Collins Circle on the western edge of downtown produced trip rates 78% below those predicted in the ITE manual.

San Francisco Bay Area – 47.5% below ITE A.M. peak rate The San Francisco Bay Area also averaged vehicle trip generation rates substantially below those estimated by the ITE manual. Among the East Bay TOD-housing projects studied, Montelena Homes had the lowest weekday rate: 2.46 trip ends per dwelling unit, 63% below ITE's rate.

Philadelphia / Newark – 30.53% below ITE A.M. peak rate Lastly, the two apartment projects near suburban commuter rail stations outside of Philadelphia and the Newark metropolitan area of northeast New Jersey averaged weekday vehicle trip generation rates that were roughly one-quarter less than that predicted by the ITE manual. This is an appreciable difference given the relatively low-density settings of these projects and that commuter rail offers limited midday and late-night services.


G.B. Arrington

GB Arrington is the Principal Practice Leader for Parsons Brinckerhoff’s PlaceMaking group. In his role he is responsible for providing strategic direction and leading PB’s global transit-oriented development (TOD) practice. He is internationally recognized as a leader in TOD. Australia’s Urban Development Institute says GB “is considered to be the world’s foremost authority on TOD policy, design and implementation.” His work has taken him across the United States, to China, Australia, New Zealand, Dubai and the Caribbean.

portrait of professional woman

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching. Mary G., Urban Planner

I love the variety of courses, many practical, and all richly illustrated. They have inspired many ideas that I've applied in practice, and in my own teaching.

Mary G., Urban Planner

Get top-rated, practical training

Bird's eye view of manufactured home park.

Manufactured Crisis: Losing the Nation’s Largest Source of Unsubsidized Affordable Housing

Manufactured housing communities have long been an affordable housing option for millions of people living in the U.S., but that affordability is disappearing rapidly. How did we get here?

March 25, 2025 - Shelterforce

U-Haul truck on road with blurred grassy roadside in background.

Americans May Be Stuck — But Why?

Americans are moving a lot less than they once did, and that is a problem. While Yoni Applebaum, in his highly-publicized article Stuck, gets the reasons badly wrong, it's still important to ask: why are we moving so much less than before?

March 27, 2025 - Alan Mallach

Close-up of rear car bumper in traffic on freeway.

Research Shows More Roads = More Driving

A national study shows, once again, that increasing road supply induces additional vehicle travel, particularly over the long run.

March 23, 2025 - Road Capacity as a Fundamental Determinant of Vehicle Travel

Aerial view of Grants Pass, Oregon with fall foliage and hills in background with a cloudy sky.

Judge Halts Enforcement of Anti-Homeless Laws in Grants Pass

The Oregon city will be barred from enforcing two ordinances that prosecute unhoused residents until it increases capacity and accessibility at designated camping sites.

6 hours ago - Street Roots

Colorful murals on exterior of Hollywood High School in Los Angeles, California against night sky.

Advancing Sustainability in Los Angeles County Schools

The Los Angeles County Office of Education’s Green Schools Symposium brings together educators, students, and experts to advance sustainability in schools through innovative design, climate resilience strategies, and collaborative learning.

7 hours ago - Los Angeles County Office of Education

Rusty abandoned oil well and equipment with prickly pear cactus next to it in West Texas.

Using Old Oil and Gas Wells for Green Energy Storage

Penn State researchers have found that repurposing abandoned oil and gas wells for geothermal-assisted compressed-air energy storage can boost efficiency, reduce environmental risks, and support clean energy and job transitions.

March 31 - Pennsylvania State University