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. 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 is a vice president and principal practice leader at PB's PlaceMaking group



Montelena Homes TOD??

"Among the East Bay TOD-housing projects studied, Montelena Homes had the lowest weekday rate: 2.46 trip ends per dwelling unit"

Where is Montelena Homes? A Google search shows developments with that name in San Diego and San Bernardino, but not in the East Bay.

Charles Siegel

Benefits Galore

Finally, hard evidence for us kool aid drinkers. Even though we know (intuitively at least) it also means less impacts on natural habitats, wetlands, biodiversity, air pollution, agricutlure and a slew of others...The health and social benefits are well documented also....Who can be against TOD now?

Interesting Results

Good thing that TOD residents never rely upon on street parking otherwise the data would be suspect.


good observation, but since codes typically require on site parking to meet the need the point here is to see what is happening at that level.

Taking the research to the next level would involve looking at turn-over rates on parking, counting walk trips and observing on-street parking. All beyond the bounds of our budget.


Thank you for the reply. I agree with all your points especially the "beyond the scope" issue. That said, my experience is that TOD always receives parking variances and I do not use "always" lightly. That must certainly have some unknowable amount effect of externalizing VPD counts.
This raises the equivalence issue. One of the supposed goals of TOD is to internalize transportation components as part of a whole project. CEQA here in California supposedly mandates this but we know how that works in practice. If CSD patterns are required to internalize/identify impacts why are we giving TOD this free pass on the same issue?

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