ITE Journal March 2018 - 45

Designing the Data Collection Plan

References

Carefully planning a road diet data collection effort, with an eye to
the way the information will later by analyzed, permits high-quality
evaluations. By contrast, without careful planning there is risk
of spending a great deal of time and money collecting data that
ultimately does not allow evaluators to assess the project impacts
with any certainly or nuance. In short, if an agency plans to invest
the money to evaluate speed and volume impacts at all, it is worth
making sure that this investment is carefully designed to get the
maximum benefit possible.
Our experience with the strengths and limitations of the
Lincoln Avenue data supports the following recommendations for
road diet evaluation plans:
ƒ Collect data on enough days to smooth day-to-day variations. A
power analysis is useful to determine the minimum amount of
data needed to perform statistical analysis.
ƒ Collect and share raw data for every vehicle instead of packaging
data into categories (to enable a wider range of analytical
approaches).
ƒ Develop a method to compare changes in traffic volumes and
speeds in the road diet area with changes outside the road-diet
neighborhood itself.
ƒ Select days for evaluation with "regular" traffic patterns.

1. Huang, Herman, F., J. Richard Stewart, Charles V. Zegeer, and Carol H. Tan
Esse. "How Much Do You Lose When Your Road Goes on a Diet?" Paper
presented at the 2nd Annual Urban Street Symposium, Anaheim, CA, 2003.
2. Lyles, Richard W., M. Abrar Siddiqui, William C. Taylor, Bilal Z. Malik,
Gregory Siviy, and Tyler Haan. Safety and Operational Analysis of 4-Lane to
3-Lane Conversions (Road Diets) in Michigan: Final Report. East Lansing, MI:
Michigan State University, January 2012.
3. Nixon, H., A.W. Agrawal, and C. Simons. Designing Road Diet Evaluations:
Lessons Learned from San José's Lincoln Avenue Road Diet. San José, CA:
Mineta Transportation Institute, WP12-14, 2017. http://transweb.sjsu.edu/
project/1629.html. Accessed January 23, 2018.

Data Analysis Approaches
To prepare this paper, we explored numerous options for different
speed and volume impact metrics, for statistical testing of the road
diet impacts, and for displaying the results graphically. Based on
this experience, we recommend conducting the data analysis and
communicating the findings as follows:
ƒ Analyze and present the impacts at each data collection location
as well as impacts by street types;
ƒ Analyze impacts by time of day as well as by all-day metrics;
ƒ Present findings about changes as both actual counts and percentages;
ƒ Design graphics that emphasize the changes between the pre
and post periods; and
ƒ Look at the numbers of "speeders," rather than mean speeds, to
identify safety outcomes.

Acknowledgments
The authors thank the many people who helped us with this project.
Particular thanks go to the City of San José staff who helped us obtain
the road diet data; James A. Bittner, P.E., senior civil engineer, and
Warren J. Navarro, transportation options graduate intern, both with
the Department of Transportation, City of San José, CA, USA. In
addition, San José State University Master of Urban Planning (MUP)
student Nicholas Danty prepared the maps, and MUP alumnus Bahar
Vaezi prepared cross-sections of Lincoln Avenue. The authors also
thank the Mineta Transportation Institute for funding the study. itej

Hilary Nixon, Ph.D. is a professor at San José State
University in the Department of Urban & Regional
Planning. She is also Director of Research and
Technology Transfer at the Mineta Transportation
Institute. Her research and teaching interests in
environmental planning and policy focus on the
relationship between environmental attitudes and behavior,
particularly with respect to waste management and linkages
between transportation and the environment. Dr. Nixon holds a
bachelor of arts from the University of Rochester in environmental
management and a doctorate in planning, policy, and design from
the University of California, Irvine.
Asha Weinstein Agrawal, Ph.D. works at San José
State University, where she is Director of the Mineta
Transportation Institute's National Transportation
Finance Center and also Professor of Urban and
Regional Planning. Her research explores effective
planning and policy tools to encourage environmentally-friendly travel and improve accessibility for people struggling
with poverty or other disadvantages. She has explored these issues
through many transportation topics, including transportation
finance policy and travel behavior research. Dr. Agrawal earned a
bachelor of arts from Harvard University, a master of science from
the London School of Economics, and a doctorate from the
University of California, Berkeley.
Cameron Simons is a researcher at the Mineta
Transportation Institute. His research interests focus
on public policy related to transportation and
housing and the field of data science. He holds a
bachelor of science in economics from San José
State University.

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M arch 2018

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