Embracing vehicle miles traveled as the traffic metric for environmental project analysis

Embracing vehicle miles traveled as the traffic metric for environmental project analysis
Apr 14, 2020

Following 2018 guidance from the Office of Planning and Research, the California Department of Transportation (Caltrans) supports using vehicle miles traveled (VMT) for transportation analysis and mitigation for land use and transportation projects. ICF’s Rich Walter and Brian Calvert explain.

On February 28, 2020, Caltrans issued a draft of the VMT-focused Transportation Impacts Study Guide(Draft TISG). On April 10, 2020, Caltrans issued drafts of the Transportation Analysis under CEQA (Draft TAC) and Transportation Analysis Framework (Draft TAF). These three guidance documents implement changes from 2013’s Senate Bill 743 (SB 743), which required a shift from using measurements of traffic delay or congestion for determining the significance of traffic impacts under the California Environmental Quality Act (CEQA), to using measurements of distance traveled, such as VMT, for most projects. VMT is a measurement of the miles driven by vehicles within a specified area over a specific time period, rather than a delay- or congestion-based metric such as level of service (LOS).

The Draft TISG guidance provides direction on CEQA analysis of VMT for land-use projects. The Draft TAC guidance provides direction on CEQA analysis for transportation projects on the State Highway System. The Draft TAF guidance provides direction on analytical methods to estimate the VMT effects of transportation projects. The comment period for the Draft TISG closed on April 10, 2020, while the comment period for the Draft TAC and TAF extends to June 15, 2020.

A new direction for land use projects

Caltrans’ Local Development-Intergovernmental Review program will use the TISG during the environmental review of land-use projects and plans. The TISG, when finalized, will replace the prior 2002 Guide for the Preparation of Traffic Studies.
The Draft TISG requires Caltrans to follow the OPR’s Technical Advisory from December 2018 when reviewing local land-use projects. Caltrans recommends the use of OPR’s suggested VMT thresholds for land-use projects and technical considerations for VMT calculation. Caltrans supports OPR’s recommended streamlining of land-use projects in transit priority areas and areas with existing low VMT (as described in the OPR’s Technical Advisory). The Draft TISG also describes potential on-site VMT mitigation approaches, drawing on options listed in the technical advisory and additional resources from the appendix to the Draft TISG. 
According to the Draft TISG, Caltrans may request targeted operational and safety analysis to address specific geometric or operational issues related to the State Highway System (or connections to the system), particularly concerning multimodal or intermodal access. While land-use development effects related to traffic congestion and delay are no longer significant impacts under CEQA per SB 743, safety issues can still be considered under CEQA.

Navigating a paradigm shift for transportation projects

As noted previously, the Draft TAC addresses how Caltrans will analyze transportation projects on the State Highway System using VMT and the Draft TAF reviews analytical approaches to estimating the VMT effect of transportation projects.

The 2018 CEQA Guidelines Update, Section 15064.3 (b)(2), grants an exception to allow lead agencies the discretion to choose the appropriate measure in evaluating the significance of transportation impact(s) under CEQA for roadway capacity projects. What this means is that VMT is not a mandatory metric for CEQA analysis of roadway capacity projects and that traffic delay metrics could be used at the discretion of the lead agency as long as they are consistent with CEQA and other applicable requirements. However, as described in the Draft TAC, Caltrans has chosen to use VMT as the primary transportation metric for CEQA analysis of projects on the State Highway System. This is a significant paradigm shift from a focus on addressing traffic delay and congestion in CEQA analysis to a focus on reducing VMT. 

The Draft TAC describes a wide range of non-capacity increasing projects not likely to result in measurable increases in VMT including the following:

  • Maintenance, rehabilitation, and repairs.
  • Turn lanes and pockets.
  • Lane reductions.
  • Grade separations.
  • Roundabouts.
  • Traffic control devices.
  • Signal timing.
  • Traffic calming.
  • Toll additions or increases.
  • New transit services.
  • Traffic wayfinding.
  • New bike or pedestrian facilities.

In addition, the Draft TAC notes that there are also some projects where the addition of pavement or lanes, the extension of lanes, or the conversion of lanes, may be involved but are, however, not likely to measurably increase VMT, including the following:

  • Road shoulder improvements for safety.
  • Auxiliary lanes less than one mile in length to improve safety.
  • General-purpose lane conversions to managed or transit lanes.
  • Transit-only lane additions.
  • Tolled lane additions (where tolls are sufficient to mitigate VMT increase).
  • Passing lanes, truck climbing lanes, or truck brake-check lanes in rural areas that do not increase overall corridor capacity.

For these projects, the Draft TAC and TAF note that a qualitative assessment will usually be adequate under CEQA, and mitigation may not be warranted. However, it should be noted that the TAC states, “When concluding that a particular project may be screened out from further analysis, the practitioner should review and fully document the rationale supporting the conclusion that the particular project would not likely lead to a measurable and substantial increase in VMT.”

The Draft TAC says that capacity-increasing projects are likely to measurably and substantially increase VMT, including the addition of through lanes on existing or new highways—such as general purpose lanes, HOV lanes, peak period lanes, auxiliary lanes, or lanes through grade-separate interchanges—and other projects adding capacity to the State Highway System. The Draft TAF describes the mechanisms by which induced travel can occur due to roadway capacity increasing projects:

  • Route changes (which may increase or decrease overall VMT).
  • Mode shift in favor of automobile use (increases overall VMT).
  • Longer trips (increases overall VMT).
  • More trips (increases overall VMT).
  • More dispersed development (increases overall VMT).

For capacity-increasing projects, the Draft TAC and TAF describe that a quantitative analysis would normally be warranted. The recommended baseline is future without project conditions. While CEQA normally considers existing conditions to be the appropriate baseline, CEQA allows for the use of future without project conditions when the project’s effects are best identified compared to such future conditions.

The Draft TAF describes two quantitative methods for estimating project effects on VMT:

  • An empirical approach applying travel demand elasticities from empirical studies that quantify the induced travel effect.
  • A travel-demand model-based approach.
The Draft TAF states that the University of California, Davis National Center for Sustainable Transportation (NCST) Induced Travel Calculator can be used for the empirical approach and is recommended for use in many urban counties for capacity-increasing projects on freeways and state routes. The Draft TAF recommends use of a travel demand model approach for capacity-increasing projects on freeways in certain urban counties, in rural counties with congestion near the project site, and for other potentially VMT inducing projects on a state route. The Draft TAF provides guidance and limitations on using these two approaches. 

The Draft TAC says that, within California areas with Metropolitan Planning Organizations (MPOs), a project that results in an increase in VMT when comparing the future with project conditions to the future without project baseline, will generally be considered significant and mitigation will be required. If the traffic impacts related to VMT cannot be mitigated to a level that is considered less than significant, a statement of overriding conditions (SOC) under CEQA may, and likely will be, needed for approval of the project. However, even if a SOC is adopted, CEQA requires that any identified feasible mitigation be implemented.  For rural (non-MPO) areas, the Draft TAC states that significance should be addressed on a case by case basis, considering context and environmental setting.

Mitigation, where warranted, may include on-site or off-site mitigation. The Draft TAC describes that it may become increasingly difficult to achieve feasible and proportional project-level VMT mitigation as a project proceeds from initial scoping to final design. That's why it's important to thoroughly consider upfront a range of project alternatives that can potentially minimize, or avoid, the additional VMT from capacity-increasing projects.

On-site mitigation on the State Highway System will often be more within Caltrans’ direct authority than off-site mitigation, as off-site mitigation is generally under the authority of agencies with influence over land use and transportation systems outside of Caltrans’ direct control. While tolling can also be an on-site mitigation strategy, it would require coordination with appropriate transportation planning agencies and may require approval of state and federal agencies as well. The Draft TAC identifies a range of other potential on-site mitigation measures including the following:

  • Incorporation of complete streets elements.
  • Incorporation of alternate modes of transportation (including bicycle and pedestrian facilities and connections to transit).
  • Park-and-ride lots.
  • Social marketing, public education, and incentives to promote trip reduction, use of transit, and carpooling.
  • Intelligent transportation systems.
  • Traffic management strategies to make bus operations more efficient and to develop a more interconnected transportation system.

When further on-site design features are not feasible or effective, the Draft TISG and Draft TAC support off-site VMT mitigation approaches. As noted above, many of these are outside Caltrans’ direct authority and will require the cooperation of many other agencies including federal, state, regional, and local entities. These approaches include, but are not limited to:

  • Land use planning.
  • Cordon (or area) pricing.
  • Parking management and pricing.
  • Employer-based transportation demand management.
  • VMT mitigation banks.
  • VMT mitigation exchanges.
  • VMT impact fee programs.

The first four approaches above are usually within the jurisdiction of local land use authorities and private development. VMT banking, exchange, or fee programs can be used to collect funding from projects with significant VMT impacts and the funds used to support VMT reducing projects such as transit, bicycle, and pedestrian projects, or other strategies.

VMT banking, exchange, or fee approaches are in the early stages of development and often take a long time to develop. But some are taking additional steps. For example, the City of Los Angeles has completed a nexus study on setting transportation impact fees based, in part, on VMT. The Draft TISG and Draft TAC also mention several useful studies of off-site banking, exchange, and fee program approaches completed by:

One thing to note: Caltrans’ use of VMT for their roadway capacity projects will not preclude other lead agencies from using traffic metrics other than VMT for determining CEQA significance for their own local roadway capacity projects. Caltrans’ use of VMT will only apply to projects where they are the CEQA lead agency. It is up to each CEQA lead agency to determine what metric they will use for roadway capacity projects.

Implementation timing 

Caltrans issued a memorandum (dated April 13, 2020) stating when State Highway System projects need to implement the use of VMT in determining traffic impacts in the CEQA analysis process. Projects that have begun their environmental phase on or after December 28, 2018, and have reached their “Begin Environmental” milestone (Caltrans’ Milestone 020) will be evaluated by Caltrans, in consultation with project sponsors, on a case-by-case basis to determine if the use of a VMT-based transportation impact significance determination in the draft environmental document is needed. This will be based on several factors, including if the project includes a new alignment and/or additional lane miles in an area with existing or projected congestion, and if there is high public and stakeholder interest in a project. 

Based on these factors, we anticipate that capacity-increasing projects in areas with existing or projected congestion are likely to require a VMT analysis. Projects that begin their environmental phase on or after September 15, 2020, will be required to complete a VMT analysis. The memorandum also provides guidance on supplemental reviews and indicates that project development teams should evaluate whether projects currently scoped as Negative Declarations/Mitigated Negative Declarations (ND/MND) may require rescoping to an EIR.

The 2018 CEQA Guidelines Update specifies that VMT is required to be used for CEQA transportation analysis after July 1, 2020, except for roadway capacity projects for which the Guidelines state that the CEQA lead agencies, "...have discretion to determine the appropriate measure of transportation impact."

Don’t forget the National Environmental Policy Act (NEPA)

SB 743 is California legislation. It does not (and cannot) remove the potential need for traffic delay or congestion analysis for projects that are also subject to the NEPA, depending on the requirements of the federal lead agency. The new Caltrans guidance is solely focused on CEQA analysis.

ICF partnering with clients on VMT analysis and mitigation

ICF actively supports clients in developing tools to analyze VMT and develop VMT mitigation, giving us hands-on insight into the challenges and solutions involved. We supported Caltrans in the development of a 2019 Literature Review and Assessment of VMT and GHG Strategies, which is included as an appendix to the Draft TAC. Another example of our work in this field is the Mobility Management Toolbox, developed with the San Diego Association of Governments. This toolbox includes: 
  • Mobility management strategies.
  • A VMT reduction calculator tool.
  • Implementation guidance.
  • Training videos.

Whatever roads CEQA transportation analysis takes us on in the future, we are closely monitoring developments and will continue to provide insights. If one thing is certain, it’s change—keeping the pulse of transportation regulation is as important as ever.


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Meet the authors
  1. Brian Calvert, Senior Managing Director, Environmental Planning

    Brian’s experience includes managing the planning and environmental work associated with a number of projects. He specializes in National Environmental Policy Act (NEPA) and California Environmental Quality Act (CEQA) analysis for projects involving the Federal Highway Administration (FHWA) and Caltrans. View bio

  2. Rich Walter, Vice President, Environmental Planning

    Rich has over three decades of experience in environmental planning, climate action planning, compliance strategy, permitting, and mitigation development and implementation for private and public sector clients.  View bio

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