Housing and VMT Mitigation

One of the more effective strategies that may be used to mitigate induced travel for transportation projects on the State Highway System is the facilitation of VMT-efficient housing projects. This type of VMT mitigation could be applied either individually during a project-level analysis or at a programmatic or regional level by tiering from a programmatic environmental document. Although the Caltrans Transportation Analysis Under CEQA (“TAC”) guidance document does encourage tiering as a strategy and the ongoing update of the RTP Guidelines by the California Transportation Commission may expand its use further, there are substantial requirements for successful implementation of the strategy that has limited its use to date. Therefore, although the use of tiering for VMT analysis and potential mitigation may be a useful tool in the future, this guidance will focus on project-level analysis.

The housing effects on VMT are well documented in the two guidance documents described below, which are included in the Caltrans SB 743 program webpage.

In 2010, the California Air Pollution Control Officers Association (“CAPCOA”) published the “Handbook for Analyzing Greenhouse Gas Emission Reductions, Assessing Climate Vulnerabilities, and Advancing Health and Equity” (the “Handbook”). This Handbook, which was updated in December 2021, included a compilation of VMT-reducing measures. While the Handbook is primarily aimed at GHG impacts, in many instances, GHG reductions can be accomplished through VMT reductions.  As such, the Handbook’s descriptions of measures and quantification are useful for considering VMT mitigation for roadway expansions.

The CAPCOA Handbook was important for the development of the July 2022 “Caltrans SB 743 Program Mitigation Playbook” (the “Playbook”). The Playbook built on the substantial quantitative procedures contained in the Handbook to provide practitioners guidance on applying the various strategies to transportation projects that are anticipated to generate induced travel.

For the topic of residential land use (i.e., density and affordability), the Playbook states:

Compact housing can reduce VMT compared to housing that is lower density. Affordable housing produces less VMT compared to market-rate housing. To the extent a project contributes to such housing, it can take credit for the VMT reduction compared to business as usual. Compared to other options, denser, more affordable housing is a powerful VMT-reduction tool.

The Playbook further notes, as an example:

If a project contributes half of the backing (funding, land, infrastructure, etc.) needed to deliver the housing units that reduce VMT by 10,000 miles/day, it could claim 5,000 miles/day as VMT reduction.

However, this section of the guidance that suggests a “proportional” VMT reduction to match the financial contribution toward the denser, more affordable housing warrants further consideration. 

When taking credit for any CEQA mitigation, as long as the mitigation is not deferred, feasible, enforceable, or meets performance criteria, a project sponsor/lead need not be the sole funding contributor to take credit for the mitigation. This is the case exemplified by in-lieu fee payments, mitigation banks, or similar exchange models whereby the project sponsor/lead does not undertake the mitigation, but instead transacts with another entity to undertake the restoration, preservation, or other mitigation action.  

Therefore, a project sponsor/lead can take “credit” for mitigation it purchases as long as the mitigation is enforceable, etc., as noted above and there is a mechanism in place to prevent “double counting” of the mitigation “credit.” With these assurances in place, a transportation project can take the full mitigation credit of a housing development if it could be shown that “but for” the contribution, the housing project would not have been developed.  These conditions and assurances would likely be included in and enforced through a funding agreement.