As a concept, induced demand is increasingly being considered by transportation practitioners at state departments of transportation (DOTs). Induced demand is challenging and intersectional, necessitating consistent analysis and transparency. DOTs are interested in understanding how induced demand impacts their planned investments and how those impacts might accrue at the local and regional network levels. It is not clearly understood in empirical analysis where induced demand manifests itself and how it undermines desired project outcomes for various project types.
Recent attempts at analysis are the California Induced Travel Calculator (CITC), the Rocky Mountain Institute’s State Highway Induced Frequency of Travel (SHIFT) tool, and the Federal Highway Administration’s Geospatial Economic Multimodal Systems Modeling (GEMS). The CITC and SHIFT tools incorporate ranges of elasticity findings from different induced demand studies and project conditions but have several limitations for project-level analysis (for example, contextual factors or land use). GEMS may provide typologies to help identify influencing factors and mitigation options as alternatives to new lane miles. Research is needed to assist DOTs to better understand induced demand, especially at the project level, concerning their priorities, policies, funding decisions, and DOT options to respond to induced demand directly or indirectly.
The objective of this research is to develop an induced demand assessment framework and a guide for DOTs to apply the assessment framework to policy and planning analysis.
At a minimum, the research shall (1) define induced demand; (2) gather and evaluate data needed to develop the assessment framework; (3) pilot, validate, and test the assessment framework; and (4) communicate findings from the framework to build consensus.
Accomplishment of the project objective will require at least the following tasks.
The sequencing of tasks and deliverables (such as technical memorandums or summary reports) shall be structured for delivery in quarterly progress report submissions. There will be three project phases, with an interim report and updated research plan due after Phase I and II. An in-person interim meeting should follow the submission of the first interim report, with a virtual meeting following the second. The research agency shall not proceed to future phases without NCHRP's approval of the interim reports and updated research plans. An estimation of time for each element of Phase I and II is presented below. However, the proposer may re-sequence the timeline according to their best thinking.
The first project phase comprises the approval of cornerstone elements of the research plan. This phase is estimated to be accomplished in two project quarters. The first project quarter shall include the delivery of (1) the Amplified Research Plan; (2) a kick-off meeting (with summary notes); (3) the definition of induced travel demand and approximate terms including, but not limited to, induced traffic, induced growth, or latent demand; and (4) a broad review of literature and practices associated with induced demand and project types.
The review of literature and practices should serve as a point of departure, and the research team shall identify gaps in methodology, their application, limitations, or opportunities. Additionally, the literature review and scan of practice should assist in identifying (1) the data to be gathered and evaluated in Phase II and (2) DOTs, metropolitan planning organizations (MPOs), or infrastructure owners and operators (IOOs) to pilot the assessment framework in Phase III.
The second project quarter should be focused on documenting the interrelationships between induced demand and factors in the short, medium, or long term, such as economic influences, elasticity of demand, scale of demand, or latent demand. Additionally, contextual influences should be explored, such as:
- Urban, suburban, and rural spaces;
- Existing connectivity or route choices;
- Proximity to environmental justice populations;
- Land costs and uses;
- Project types and different project scales (on existing facilities, operational or capital improvements);
- Availability or provision of mode choice; and
- Existing policies (for example, adjacent land use, reducing greenhouse gases, or vehicle miles traveled).
It is envisioned that this step will later assist with developing the assessment framework in Phase II.
To complete the second project quarter, the research team shall deliver the first interim report and updated Phase II research plan with an in-person interim meeting. One month shall be reserved for review and NCHRP approval.
The project's second phase shall be focused on gathering and evaluating data on a range of project types on existing facilities for developing an induced demand assessment framework. This phase is estimated to be accomplished in three project quarters. The assessment framework should enable a structured and transparent way to evaluate the relative potential for generating induced demand linked to contextual factors and illustrate effects on DOT desired outcomes resulting from various improvements. Finally, the assessment framework should indicate the order of magnitude project-level induced demand.
In the third quarter of Phase II, the research team shall deliver the second interim report, including the draft assessment framework and updated Phase III research plan. The updated research plan shall propose the format and outline for the guide to the assessment framework requested in the final deliverables. A virtual interim meeting will be held following panel review of the second interim report. One month shall be reserved for review and NCHRP approval.
The third phase shall not exceed three project quarters and be reserved for piloting the assessment framework and developing the final deliverables.
In the sixth project quarter, the research team shall conduct a minimum of three pilots with volunteer DOTs, MPOs, or other IOOs to validate the assessment framework. A diversity of agencies should be sought to reflect the different planning and policy contexts of agencies. The research team shall propose the agencies for pilots in the updated Phase II research plan for panel review and NCHRP approval. These pilots should inform the development of educational and training materials in Phase III. A task report shall document opportunities, challenges, barriers, and other observations learned from the pilots useful for refining the assessment framework.
The final draft guide shall be delivered at the conclusion of the seventh project quarter and according to the approved updated Phase III research plan. Final deliverables shall include:
- A guide to the assessment framework presented in Microsoft Word;
- Educational materials or training resources targeted to DOT practitioners (planners and those engaged with the National Environmental Policy Act), DOT leadership, and DOT partners to increase shared understanding of induced demand and build consensus;
- A conduct of research report (including future research needs and technical appendices or data as needed);
- A PowerPoint presentation with speaker notes that summarize the project and distinctly illustrate for the audience how the research can be applied in their organization;
- A draft article suitable for publication in the TR News (no guarantee of publication is implied); and
- An implementation plan.
STATUS: Proposals have been received in response to the RFP. The project panel will meet to select a contractor to perform the work.