VMT 101
VMT Definition
Vehicle Miles Traveled (VMT) is a key metric for traffic policy and engineering, providing a comprehensive aggregation of the distance traveled by motor vehicles within a specific geographical area over a defined time frame, typically a year. A region’s VMT is measured as the collective mileage accrued by all vehicles operating within that region, regardless of the number of passengers they carry.
Projects that increase the number of cars on the road or the distance those cars travel will increase VMT. Projects or programs that encourage transit ridership or active transportation will reduce VMT by taking cars off the road. Smart land use planning can also reduce VMT by reducing the distance each vehicle must travel to reach its destination.
Total VMT does not factor in passenger occupancy, so a carpool carrying five passengers 4,000 miles annually would produce the same VMT as a solitary driver covering the same distance. The VMT per capita of the carpool vehicle, however, would be only 1/5th of the solo driver’s car. In many cases, including when analyzing a proposed project’s environmental impacts, VMT per capita and other VMT efficiency measurements can prove far more insightful than total VMT.
VMT Importance
California has set ambitious goals for statewide greenhouse gas emissions in order to avert the worst impacts of climate change. SB 32 (Pavley, 2016) requires CA to reduce GHG emissions 40% below 1990 levels by 2030.
Clean vehicles and clean energy alone will not be enough to achieve this. Even if California attains 100% zero emission vehicles (ZEVs) and 75% of its energy from renewable sources, we will still need a 15% reduction in VMT to meet our climate targets.
Co-Benefits
VMT reduction also provides significant co-benefits that traditional decarbonization doesn’t – air quality, habitat conservation, natural resource protection, social equity, and livable communities.
Every car on the road generates air pollution. ZEVs eliminate tailpipe emissions (CO2, NOx, etc.), but they still generate particulate matter – a known carcinogen – from brake, tire, and road wear. Reliance on ZEVs without reducing single-occupant travel pollutes our air and endangers frontline communities near roadways.
When we implement policies that reduce VMT, we also reduce the number of cars on the road. Trains, buses, carpools, bikes, and pedestrians all generate much less particulate matter per passenger. Even where car use still dominates, land use planning that reduces commute lengths can significantly reduce VMT and have major benefits for air quality.
Car-oriented development encourages suburban sprawl and development of the wildland-urban interface (WUI), threatening the remaining habitat of California’s precious biodiversity.
In order to reduce long car commutes and incentivize active transportation, VMT-oriented land use planning prioritizes brownfield development (or infill) over greenfield development. By focusing building activity within existing developments instead of expanding outward, reducing VMT goes hand-in-hand with vital conservation.
High-VMT planning makes infill housing far less affordable, displacing low-wage workers from transit access. Many are forced to move to the urban periphery in search of affordable housing, creating long commutes and extremely high fuel costs. Additionally, the harms of unmitigated air pollution from rising VMT are felt most heavily by those living near major roadways, who are frequently low-income households and communities of color.
Prioritizing VMT reduction in land use planning aims to preserve jobs-housing fit, so that workers do not have to travel as far to reach relevant economic opportunities. In order to preserve this, VMT-conscious planning protects affordable housing located near transit and economic opportunities. These protections prevent the displacement of low income households to the urban periphery and high-pollution areas, keeping communities and cultures together. Read more about displacement here.
Low-VMT planning creates walkable communities with nearby access to transit, groceries, and economic opportunities. Bike and pedestrian infrastructure keeps people healthy, walkable local services promote neighborhood interactions, and protection from displacement preserves local history and culture. Low VMT communities are happy, healthy, and vibrant places to work and live.
Policy and Future
The passage of SB 375 (2008) and SB 743 (2013) took the first major steps towards rethinking our transportation planning by requiring projects to identify and mitigate VMT increases in CEQA reviews. Yet, despite broad recognition of this need, CARB’s modt recent 2018 Progress Report on SB 375 (2008) implementation has illustrated that per capita VMT is going up in California, not down, and none of the State’s regions are on track to achieving their respective GHG reduction targets through improved land use and transportation (reduced VMT) as mandated by SB 375. We need to prioritize land use planning that supports our VMT reduction needs and prevent induced car usage to keep our climate goals within reach.