AASHTO STANDING COMMITTEE ON RESEARCH
AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS
NCHRP Problem Statement Outline
I.
PROBLEM NUMBER
To be assigned by NCHRP staff.
II.
PROBLEM TITLE
Evaluate the Potential Benefits of Roadside Trees to Reduce Greenhouse Gas Concentrations and
Improve Water Quality
III.
RESEARCH PROBLEM STATEMENT
Air pollution reduction and water quality protection are critical public health and ecologic
challenges facing Departments of Transportation (DOTs) throughout the country. DOTs are
obligated to meet environmental requirements mandated by legislation such as the Federal Clean
Air and Water Acts and to develop flexible, long-term and cost effective strategies to meet these
regulatory requirements. To expand the toolbox of strategies there is a need to understand the
environmental and economic value of the air pollution removal capacity and the stormwater
treatment benefits of existing and new trees in the state right-of-way. Trees are proven
mitigation measures that sequester carbon, shade impervious surfaces, function as non-structural
stormwater management facilities, and improve erosion control and groundwater recharge.
Many DOTs are considering the implementation of extensive tree planting programs as a
response to climate change without a complete understanding of best practice strategies.
IV.
LITERATURE SEARCH SUMMARY
American Forests. ‘Trees and Ecosystem Services’,
http://www.americanforests.org/resources/urbanforests/naturevalue.php
Caltrans Division of Environmental Analysis, 2003. ‘Roadside Vegetated Treatment Study’,
http://www.dot.ca.gov/hq/env/stormwater/pdf/CTSW-RT-03-028.pdf
McPherson, E. Gregory; Simpson, James R. (1999) ‘Carbon Dioxide Reduction Through Urban
Forestry: Guidelines for Professional and Volunteer Tree Planters’,
http://www.fs.fed.us/psw/publications/documents/psw_gtr171/
West Coast Regional Carbon Sequestration Partnership, 2006. ‘Terrestrial Storage’,
http://www.westcarb.org/terre_storage.htm
V.
RESEARCH OBJECTIVE
Using tools such as GIS and urban forestry software, a consultant would synthesize existing data
and conduct statistical analyses to determine the economic and environmental value of air
pollution removal and stormwater treatment benefits provided by trees in the right-of-way.
Existing research on this issue has concentrated on the value of extremely large tracts of forest
lands to provide ecologic benefits. Information is needed on the potential benefits of liner forests
adjacent to the highway environment. Many DOTs have implemented vegetative roadside storm
water treatments using grasses, low-growing shrubs and groundcovers. There is a need to
understand how trees fit into the equation. Research will identify environmental benefits
provided by trees, identify agencies (state, national and international) that have successfully
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developed similar programs, and draft strategic plans and business plan models to implement
recommended guidance.
VI.
ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD
It is estimated that the proposed research will require $450,000 and 36 months to accomplish,
including three months for preparation of a draft final report.
VII.
URGENCY, PAYOFF POTENTIAL, AND IMPLEMENTATION
Quantifying the air pollution removal and stormwater treatment services provided by trees will
assist DOTs in developing cost effective practices to meet Federal clean air and water regulations
and making better land use decisions to assist in the reduction of global climate change.
VIII.
PERSON(S) DEVELOPING THE PROBLEM
Keith Robinson, ASLA
Principal Landscape Architect
State of California Department of Transportation
Landscape Architecture Program, Mail Station 28
1120 N Street
Sacramento, CA 95814
Phone: 916-654-6200
Email: keith.robinson@dot.ca.gov
Barbara Petrarca, ASLA
(Chair, TRB AFB40)
Supervising Landscape Architect
Rhode Island DOT
2 Capitol Hill
Providence, RI 02903
Phone: 401-222-2023 x 4090
Email: bptrarca@dot.state.ri.us
IX.
PROBLEM MONITOR
The problem will be monitored by a representative of TRB Committee AFB40 and a
representative of Caltrans, inclusive of the individuals mentioned above under Section VII.
X.
DATE AND SUBMITTED BY
This research problem statement is hereby submitted on 9/15/08 by the Rhode Island Department
of Transportation.
Please submit completed problem statement to the following e-mail address:
nchrp@nas.edu
Questions on the process can be directed to the same address or cjencks@nas.edu.
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