An aerial view of a multifamily housing complex next to a road
Jul 10, 2019
Photo by cegli
Kelly Clifton, Portland State University

Many cities are reconsidering their reliance on ITE's Trip Generation Manual, now in its 10th edition. 

Kelly Clifton, TREC researcher and associate dean for research of Portland State University's Maseeh College of Engineering & Computer Science, is one of the people leading the charge to identify better, more nuanced ways to anticipate transportation demand; especially person (non-car) trips. In an extended series of TREC projects, Clifton...

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Kelly Clifton and student - presenting research at TRB Annual Meeting
Jan 02, 2019
Principal Investigator: Kelly Clifton, Portland State University
Research spans multiple studies and years of work.
This content was originally published in the June 2018 edition of the  U.S. DOT UTC Spotlight series (PDF).

University Transportation Center (UTC) Spotlight

In recent decades, cities have become increasingly motivated to invest in infrastructure that supports multimodal options like walking, biking and public transit. Trip generation, the first step in conventional four-step forecasting models, is a central figure in determining how those investments are made.

However, when considering pedestrian and bicycling travel, the current practice is usually to either leave those trips out of the model altogether, or to simply present them as a mode choice option that is not analyzed further. In short, they’re car-centric.

Without reliable trip generation rates for anyone but drivers, an accurate transportation impact is difficult to predict. Certain land uses will draw far more walkers, cyclists and transit riders than drivers. Cities lack enough information to strategically plan for multimodal...

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Mar 28, 2017

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Many agencies rely on trip generation estimates to evaluate the transportation impacts of land development in urban and suburban areas alike. Over the past decade, substantial attention has been paid to one national set of guidelines—the Institute of Transportation Engineers (ITE) Trip Generation Handbook (2014) and corresponding Manual (2012)—focusing in particular to improve the use of these data and supplementary methods for urban contexts. 

The purpose of this study is to explore the typical data provided in the Handbook, within the context of these new improved state-of-the-art methods. As ITE’s describes, “an example of poor professional judgment is to rely on rules of thumb without understanding or considering their derivation or initial context” (Institute of Transportation Engineers, 2014, p. 3). This research aims to improve the understanding of these data—still ubiquitously used across the US—to encourage increased engagement with their meaning, and following, to provide the users (e.g., engineering, planners, agencies, and developers) with the landscape from which these data were collected and for which they represent. From here, more informed decisions can be made about whether these data provide an adequate or accurate estimation transportation impacts within varying contexts and applications.

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Feb 27, 2017

The city of Portland is using research and expertise from TREC researchers to change how it calculates fees for new development. Developers pay the fees, called transportation system development charges, to offset some of the costs of providing transportation infrastructure.
 
The foundation for those fees has been cars: that is, how many car trips a development will generate. In December, the Portland City Council voted to instead use “person trips” as the basis for those fees.
 
Researchers Kelly Clifton and Kristina Currans have assembled an impressive portfolio of research projects on trip generation. Their research caught the attention of city officials, who brought Clifton and Currans in as consultants to help them rethink the way they assess new fees for development.
 
Their work found a receptive audience of practitioners at TREC’s flagship conference, the Transportation and Communities Summit, last fall. Clifton and Currans held a workshop on improving trip generation methods to better represent the mix of modes found in livable communities. That led to a collaboration with transportation consultants...

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Feb 07, 2017

A new NITC report offers a multimodal framework for transportation impact analysis – a welcome tool for professionals in many cities seeking more detailed data about non-drivers.

Improving Trip Generation Methods for Livable Communities, a research project headed by Kelly Clifton of Portland State University and Nico Larco of the University of Oregon, is the latest effort in an ongoing collaboration to create more open sourced, widely available data about non-motorized road users.

Over the last decades, cities have become more invested in fostering the conditions to support walking, biking and public transit.

The land development process presents a unique challenge.

Prior to a zoning change or new development, someone has to determine what its impact on the transportation system will be, and whether upgrades will be necessary to accommodate travelers to the new destination. Trip generation is the first step in the conventional transportation forecasting process.

Current trip generation methods used by engineers across the country tend to focus on motorized modes.

Without reliable trip generation rates for anyone but drivers, the transportation impact is difficult to predict. Certain land uses will draw far more walkers,...

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Jan 18, 2017

Smart Growth America hosted a webinar Jan. 31 on NITC research finding that standard guidelines lead to a drastic oversupply of parking at transit-oriented developments. That restricts the supply of housing, office and retail space while driving up the price.

The webinar marks the release of Smart Growth America's lay summary of the NITC report, called "Empty Spaces," which will be available to webinar attendees.

Watch the recorded webinar here.

The research, led by Reid Ewing of the University of Utah, is one of the first comprehensive data-driven reports to estimate peak parking and vehicle trip generation rates for transit-oriented development projects, as well as one of the first to estimate travel mode shares for TODs. Ewing analyzed data on actual parking usage and total trip generation near five transit stations: Redmond, Washington; Rhode Island Row in Washington, D.C.; Fruitvale Village in Oakland, California; Englewood, Colorado; and Wilshire/Vermont in Los...

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Feb 10, 2014
OTREC research has taken steps toward developing trip generation rates for sites in a multimodal context.
Trip generation refers to the number of vehicle trips that are predicted to originate in a particular zone. The Institute of Transportation Engineers (ITE) provides standard trip generation rates, but these rates are primarily measured in low-density suburban areas.
In areas that have a more compact urban form, better access to transit and a greater mix of land uses, fewer (and shorter) vehicle trips might actually be generated there than the current ITE rates indicate.
A project headed by Kelly Clifton, of Portland State University, examines the ways in which urban context affects vehicle trip-generation rates across a variety of land uses.
 
Results from this study reveal a trend: For all land uses tested, vehicle-trip rates decrease as neighborhood types become more urban.
There is a strong industry bias toward using ITE-published rates, so that when local governments are evaluating transportation impacts and calculating transportation system development charges, they are often compelled to use the ITE rates...
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