Rural Counties Task Force presents induced‑demand study, recommends hybrid analysis and screening criteria

Mike Whitman, executive director of the Nevada County Transportation Commission and project manager for the Rural Counties Task Force induced‑demand study, presented study findings and recommendations to the Transportation Commission webinar.

Whitman said the Rural Counties Task Force commissioned the study to determine whether the elasticity‑based methods used in many induced‑travel tools are appropriate for rural, non‑metropolitan counties. The study team—led by DKS Associates and GHD Inc. with academic collaboration from Cal Poly—reviewed literature, project case studies and interviews with drivers to test applicability in rural corridors.

“Project location and context are critical to correctly identifying potential impacts under CEQA,” Whitman said. He described rural corridor characteristics: congestion in rural corridors tends to be short, peak‑period congestion rather than chronic suppression of latent demand; many rural projects are driven by safety, goods movement or evacuation needs rather than congestion relief; and rural projects often do not provide new access to developable land because they cross protected lands or federal forest areas.

Because empirical elasticities underpinning tools such as the NCST calculator are largely drawn from urban studies, the Rural Counties Task Force concluded those elasticities may overestimate induced VMT in many rural non‑MSA corridors. The study therefore recommends a hybrid methodology: use travel‑demand models to estimate the short‑run induced effect captured by behavioral responses (route choice, time‑of‑day shifts, mode shifts) and an elasticity‑based tool (for example NCST) to estimate the long‑run portion of induced demand tied to land‑use changes.

Whitman described a proposed screening flowchart: screen projects for recurring, extended congestion that suppresses latent demand; check whether the project reduces travel time by a substantial threshold (the study’s interview‑based materials referenced a 15‑minute travel‑time reduction as a level where drivers reported notable destination changes); and evaluate whether the project is likely to enable land‑use change. If answers are no, projects could be screened out of long‑run induced‑demand analysis.

The study also recommended improvements to NCST‑style tools, including more flexible interfaces, context‑sensitive inputs and additional factors that drive induced responses, and urged coordinated data collection to strengthen rural evidence. Whitman said the task force will coordinate with Caltrans, CAPTI implementation teams and university research partners to test and implement study recommendations.

Whitman noted the rural non‑MSA counties together generate a small share of statewide VMT (about 4% per 2020 public roads data), and many rural counties show static or declining population trends—factors the report said should be considered when estimating long‑run VMT effects.