Study: Self-Driving Cars Could Raise VMT by 6%, Increasing Congestion

Why It Matters

The findings challenge the optimistic narrative that AVs will ease congestion, indicating that policymakers must address potential traffic and fiscal impacts before widespread deployment.

Key Takeaways

• Autonomous shift could raise U.S. VMT by roughly 6%
• Shared robotaxis may increase VMT even more than private AVs
• Higher VMT risks severe congestion and reduced fuel tax revenue
• Safety and equity gains offset by added car dependency
• Urban sprawl could intensify as travel becomes easier

Pulse Analysis

The University of Texas‑Arlington study adds a sobering data point to the autonomous‑vehicle debate, quantifying a 6% rise in vehicle miles traveled when cities adopt self‑driving cars at scale. This increase stems not only from private AV ownership but also from shared robotaxis that spend considerable time traveling empty between passengers. The analysis underscores that the efficiency of algorithmic routing does not automatically translate into fewer miles on the road; instead, the convenience of on‑demand mobility can encourage longer trips and more frequent trips, amplifying congestion in already crowded urban corridors.

For city planners and transit agencies, the implications are two‑fold. First, higher VMT threatens to erode traditional fuel‑tax revenues that fund road maintenance and public transit, potentially deepening budget shortfalls for agencies already grappling with ridership declines. Second, the projected congestion could offset safety and equity benefits touted by AV proponents, as slower traffic flow diminishes the net time savings for users. Policymakers may need to reconsider zoning, parking requirements, and congestion‑pricing mechanisms to mitigate the extra mileage and preserve the fiscal health of transportation systems.

To harness autonomous technology without exacerbating traffic woes, jurisdictions should pair AV rollout with robust regulatory frameworks. Strategies might include mandating minimum occupancy thresholds for robotaxis, incentivizing electric‑powered fleets to curb emissions, and integrating AV data streams into real‑time traffic management platforms. By aligning autonomous mobility with broader sustainability and equity goals, cities can better balance the promise of safer, more accessible travel against the risk of super‑charging vehicle miles traveled.