The State of California has enacted ambitious policies that aim to reduce the state’s greenhouse gas (GHG) emissions. Some of these policies focus on reducing the amount of driving throughout the state, measured in vehicle miles traveled (VMT), given that transportation, primarily automobile use, is the largest single source of California’s GHG emissions. To encourage local plans and projects that reduce VMT, California has established several grant programs to which local jurisdictions may apply.
These grant programs have generated a need for methods to estimate the potential VMT – and thus GHG – impacts of proposed planning efforts, land development projects, and transportation projects. Many VMT estimation methods are available today, ranging from regional travel demand models to spreadsheet-based calculations. The simpler “sketch” models have emerged to assist local jurisdictions and planning departments in measuring the VMT effects of land use decisions, and vary in their approach and appropriateness for the breadth of potential development projects and project locations. This has left practitioners with an open question as to which method to use for a particular project and little empirical information to guide their decision.
In this report, the researchers compare and evaluate VMT estimation tools across a sample of land use projects. They compare the results from different tools for each project, consider the applicability of methods in particular contexts and for different types of projects, and assess data needs, relative ease of use, and other practical considerations.