American Association of
State Highway and Transportation Officials
Special Committee on
Research and Innovation
FY2023 NCHRP PROBLEM
STATEMENT TEMPLATE
Problem Number:
2023-B-20
Problem Title
DOT
Guidance on Induced Demand Effects of various Roadway Investments
Background Information and Need For Research
Operational
improvements such as auxiliary lanes and intelligent transportation system
treatments are designed to reduce congestion. Even these minor congestion
improvement strategies and investments intended to optimize existing roadway
system assets are increasingly facing opposition in the name of “induced
demand”, often pointing to potentially disparate impacts on Environmental
Justice (EJ) communities. The public
raises concerns about increased greenhouse gases (GHG) and air quality impacts
of such projects and lack trust that the traffic analyses are accurately
accounting for induced demand. The concern has been used as a cudgel to suggest
that even historically understood congestion improvement activities may
actually be hurting, rather than helping, the air quality of the commuting and
near-road communities. DOTs need
assistance in understanding the best investments in lieu of induced demand to
reduce roadway congestion.
Recognizing
even operational and safety improvements may have some level of induced demand,
and induced demand makes it more difficult to build our way out of congestion,
DOTs are planning such investments and need to better understand their
potential unintended consequences. Some data have shown substantial reductions
in congestion with auxiliary lanes by reducing conflicts in complex weaving
areas, brings these segments back up to their theoretical capacity. However, results
are complicated by changes in travel patterns (re-routing, time of day),
measuring reductions in incidents, and capturing safety impacts on parallel
local roads and alternative modes. Even auxiliary lanes less than one mile to
remove bottlenecks, which EPA has explicitly identified as exempt from
conformity in their last PM Hot-Spot FAQ, now have had public concerns raised
regarding their potential to induce demand.
These challenges call for consistent analysis and transparency.
Most
induced demand research is tied to significant new lane-mile capacity changes
and has often been theoretical. Limited research has evaluated the real-world
effects of these smaller roadway treatments, leaving key questions unanswered:
• Under what conditions do major and minor
induced demand issues occur?
• Does the induced demand counteract
the congestion improvement entirely or even substantially?
• Can these effects be mitigated
(e.g., through tolling or land use controls, etc…)?
• How can roadway improvements be a responsible
component of a transportation system with regards to tacking air quality and
GHG emissions?
A
definitive study of these and other minor capacity enhancements on both
freeways and arterials, as well as mitigation options is needed to improve DOT investment
decisions for the long term and enable more productive conversations with the
public.
Literature Search Summary
Recent
research, such as that supporting the new Caltrans Induced Demand Tool, have
incorporated ranges of elasticity findings from different induced demand
studies and project conditions. However the literature has less to say about
the influencing factors and mitigation.
The literature also focuses on larger capacity projects, and assume
those relationships scale to much smaller projects where the perceived benefit
to a user may be negligible. The
proposed effort should build on a research-based usage of the term “induced
demand” and its many variants, to provide nuance to the colloquial public usage
and establish definitions that distinguish induced demand effects from small to
large roadway investments. In order to develop a methodology to determine
overall congestion changes and fill gaps in the literature, the research will
need to evaluate and build on existing research on operational and minor
capacity enhancements.
Research Objective
To
provide confidence to both the travelling public and near-road communities
(including EJ communities) that DOTs are taking the induced demand concern
seriously and to implement roadway enhancements that are truly beneficial to
them by:
• Perform a literature review, that
informs the Assessment Framework, isolated new analysis, and outreach
materials:
• Create an Assessment Framework that
would:
o Definitions. Defines induced demand in
a consistent way, i.e. between build and no-build future scenarios, and covers
the spectrum of projects, i.e. large capacity enhancements to smaller
operational improvements.
o Evaluation. Enable a structure way to
evaluate the relative potential for generating typical induced demand “effects”
resulting from various “project types”; and how those effects impact agency
“outcome areas” such as air quality and climate, teasing out significant
differences in effects across project types. Definitions and evaluation
framework should be reviewed with selected outside reviewers prior to
finalization.
o Factors & Mitigation. Identify
contextual factors that alter potential latent and induced demand (i.e., base
travel cost, land use, tolling, and improved local street connectivity). These
factors should be supported with examples in practice.
o Analysis Best Practices. Identify Best
Practices in modeling & analysis to capture the effects defined above
consistently.
• Create and implement isolated new
research (analysis and/or modeling) to fill Assessment Framework gaps.
Preference is for observed over modeled theory; anticipate gaps in smaller ITS,
auxiliary lanes, operational projects.
If modeling is used, air quality models may be unnecessary as
improvements can be assumed if congestion improvements are demonstrated.
However, evaluation of network models may be important to evaluate overall VMT
and associated congestion changes.
• Create and pilot outreach materials,
build on latest behavioral science on changing attitudes, including:
o Guidance. Develop materials to clearly define the
various induced and latent demand causes and effects, typical project induced
effects and mitigation options using the assessment framework. Case study
examples will provide narratives to communicate complexities.
o Lookup Tool. Provide a lookup tool by
which DOTs can match combinations of project types, treatments, and mitigation
actions that will best meet various congestion circumstances to lead to desired
public goals (i.e., congestion, air quality improvement)
o Pilot Implementation. Coordinate with
a few DOTs to apply the outreach materials process in a couple locations,
(urban/rural project applications by different DOTs), to assess how it affects
relationship with the public on the project.
Urgency and Potential Benefits
The
public and interested groups are using induced demand arguments to oppose new
roadway investments and small operational and safety roadway projects by DOTs
across the country. In order to invest responsibly – balancing safety,
economic, equity, and climate concerns – DOTs need to better understand the
actual effects of these projects, especially of smaller roadway treatments and
other mitigation options. Additionally, with tough tradeoffs, DOTs would engender
more public buy-in through more nuanced discussions grounding in understandings
of comparisons with other areas of the country. Ultimately this study would
provide a broader understanding of effective roadway congestion strategies, and
would help DOTs avoid investing tax dollars in projects/treatments that if left
unmitigated are unlikely to achieve their intended goals.
Implementation Considerations
The
proposed study includes a peer exchange to draw on the experience of the states
that already consider induced demand and development of new resources to be
most helpful to state DOTs as funds allow. The contractor would give a
presentation of the final product to AASHTO’s AQCCES committee. The new
resources would be implemented by individual state DOTs, which could customize
the materials to their specific needs (types of projects, resident concerns,
etc.). DOT planners, project delivery coordinators, NEPA practitioners, and
other DOT staff engaging with the public throughout transportation project development
and delivery would be responsible for utilizing the results of this research
and for integrating the methods of analysis and framework definitions into
their existing business practices and communications strategies. Interested
DOTs could use this research and the resulting tools to:
• Better capture and analyze potential
for induced demand associated with proposed transportation projects using best
practice analysis methods designed to consistently analyze and quantify
measurable differences in induced demand between projected future build
congestion and projected future no-build congestion as part of transportation
project planning and design.
• Based on analysis results, determine
the appropriate level of mitigation needed where project evaluation identifies
high potential for induced demand as a result of the project as proposed.
• Improve public conversations about
this issue and how potential impacts are factored into project considerations,
to better distinguish the potential for induced demand that stems from issues
unrelated to a specific transportation project i.e. planned land use, human
behavior influences (e.g. gas prices, economy, alternative choices).
• Best practices analysis methods that
consistently capture the various induced demand effects, i.e. tool feedbacks,
comparison of build and no- build future scenarios.
Recommended Research Funding and Research Period
Cost
estimate for the workplan (#5), including pilot efforts of final communication
materials.
$250k
for 18-month effort, assuming last 6 months for DOT pilot usage
Problem Statement Author(S): For
each author, provide their name, affiliation, email address and phone.
Tara
Weidner, Oregon DOT-Climate Office,
Tara.J.Weidner@odot.state.or.us, 503-986-4226
Katherine
Silva, Oregon DOT-Climate Office,
Katherine.SILVA@odot.state.or.us, 503-986-3495
Tim
Wood, Texas DOT - Environmental, Tim.Wood@txdot.gov, 512-416-2659
Potential Panel Members: For each panel
member, provide their name, affiliation, email address and phone.
Robert Bertini, Oregon State University, Civil & Construction Engineering,
School Head/Professor, robert.bertini@oregonstate.edu, 541-737-5682
Susan Handy, University of California at Davis, Department of Environmental
Science and Policy, Professor, slhandy@ucdavis.edu , 530-752-5878
Alexander Bigazzi, University of British Columbia, Dept. of Civil Engineering
and School of Community and Regional Planning, Associate Professor,
abigazzi@civil.ubc.ca, 604-822-4426
Tim Wood, AASHTO Air Quality, Climate Change & Energy Subcommittee member,
Texas DOT - Environmental, Tim.Wood@txdot.gov, 512-416-2659
Person Submitting The Problem Statement:
Name, affiliation, email address and phone.
Tim
Hill, CES Vice Chair, 614-644-0377, Tim.hill@dot.ohio.gov ,
Affiliations:
Ohio DOT & AASHTO Committee of Environment and Sustainability