Annotated Bibliography - SSTI

Title
Traffic Generated by Mixed‐Use Developments—Six‐Region Study Using Consistent Built
Environmental Measures
Authors
Reid Ewing, Michael Greenwald, Ming Zhang, Jerry Walters, Mark Feldman, Robert
Cervero, Lawrence Frank, and John Thomas
Sponsor Reconnecting America
Date December, 2009
Pages 21
Category Development, Modes: All
Note New method for calculating traffic from mixed use development.
Online
Summary
http://www.reconnectingamerica.org/assets/Uploads/trafficmixedusedevelopments20
09.pdf
This study develops a new methodology for predicting traffic impacts in mixed used
developments as contrasted with the standard method recommended by ITE. The ITE
method is based on experience at 6 multiuse sites in Florida. The researchers chose
mixed use developments (MXD) in 6 regions that had high quality data available that
met these two criteria:
• regional household travel surveys with XY coordinates for trip ends, so we could
distinguish trips to, from, and within small MXDs; and
• land use databases at the parcel level with detailed land use classifications, so landuse
intensity and mix could be observed down to the parcel level.
The authors found only 13 regions that met the first criterion and only six regions:
Houston, Boston, Atlanta, Portland, Sacramento, and Seattle that met both. These six
provided for a research base of 239 MXDs. The internal capture, non‐auto rate for all
trips averaged 29%, with the external walk and transit shares varying considerably
among MXDs and the cities. Boston had the highest average external (from
development) walk rate at 13.2%, with Seattle having the highest external transit rate
at 8.7%, as shown below:
Walk Transit
Atlanta 3.2% 2.1%
Boston 13.2% 3.7%
Houston 2.7% 5.2%
Portland 7.1% 3.3%
Sacramento 1.8% 0.2%
Seattle 4.7% 8.7%
External auto trip distances among the regions also varied substantially, with the
average distances among all of 7.5 miles. The range was from 4.8 miles for MXDs in
Boston to 13.6 miles for MXDs in Houston.
The analysis shows that mixed‐use developments reduce traffic impacts compared to
conventional development – 3 out of 10 trips produced or attracted to an MXD pose no
burden to the street/roadway system. They also generate walking and transit trips, and
shorten vehicle trips.
Annotated Bibliography Page 14