Performance Indicator Spotlight: Vehicle Miles Traveled
One of ways we track progress toward achieving goals in the 2050 Regional Development Framework is to measure how much people in the region drive. This measure, Vehicle Miles Traveled, or VMT, is one of the Framework’s “performance indicators.”
What does VMT specifically measure and where does it come from?
Total VMT is a measure of total miles traveled by motor vehicles per day. VMT is also expressed per-household or per-person to understand the amount people drive, separate from the effect of population change.
Why do we track VMT? What does it have to do with goals in the Framework?
CARPC’s Regional Development Framework promotes development that:
- Reduces greenhouse gas emissions and fosters resilience to climate change
- Increases access to jobs, housing, and services for all people
- Conserves farmland, water, natural, and fiscal resources
The Framework aims to achieve those goals through a set of objectives including “increase the percent of development that is compact, mixed, walkable, and where feasible, transit supportive.” The Framework further recommends three growth strategies to realize that objective:
- Focus growth in centers and corridors
- Prioritize growth in already developed areas (also known as infill development)
- Plan complete neighborhoods
Carrying out these strategies and generating more compact, mixed, walkable areas will reduce driving, or VMT. Bringing people closer to desired destinations results in shorter car trips and more travel by walking, biking, and transit. Thus, lower VMT indicates progress towards regional goals because:
- Less driving means less tailpipe emissions of greenhouse gases.
- Shorter car trips and more walking, biking, and transit saves people money and make it easier to get to jobs, services, and other destinations.
What does VMT tell us about progress towards our goals?
Tracking VMT trends tells us whether we are heading in the desired direction of decreasing VMT. As shown in the blue bars on the chart below, total daily VMT in Dane County increased over the last decade until the pandemic forced people to stay home in 2020. It bounced back in 2021 as people got vaccinated but was still less than pre-pandemic highs.
The orange line shows that daily VMT per household was flat through the last decade before dipping during the pandemic. This means that the rise in total VMT was due to increasing population and not to people driving farther. The pandemic caused us to drive less but travel seems to be returning to similar levels. An outstanding question yet to be answered is whether the sharp rise in telecommuting, which continues today, will reduce VMT long-term.
Where do we want VMT to be? What level of VMT would be considered a success?
One answer comes from the Dane County Climate Action Plan (CAP), which sets a goal to reduce total VMT 15 percent by 2050. According to the CAP, we need to both transition to electric vehicles powered by renewable energy and reduce VMT to meet net zero greenhouse gas emissions.
A 15 percent reduction means dropping from 12.0 million to 10.2 million daily VMT. With an anticipated 200,000 more people by 2050, per-household VMT will need to drop by significantly more than 15 percent. Achieving such VMT reductions will take more than the strategies recommended in the Regional Development Framework. It will also require new investments and policies to encourage alternative modes of travel.
Another answer to the question of where we want VMT to be comes from looking at the cost of car travel. Car ownership and travel costs are burdensome to many families in the region. More options to live in areas closer to destinations that can be reached by walking, biking and transit can reduce transportation cost burdens.
For example, a Dane County family with average income, living in an area that requires them to drive to almost all destinations, may spend 20 percent of their gross income on transportation. Even if their housing at that location is affordable (30 percent of income), half of their income is spent on the combined costs of transportation and housing, a significant burden. In fact, just over half of households in the county (51 percent) spend more than 45 percent of their income on housing plus transportation costs – past the threshold considered to be affordable.[1]
Reducing per-household VMT will reduce housing plus transportation cost burdens. The average household in the county drives about 46 miles a day. Households in Multnomah County (Portland, OR), one of the Madison area’s peer regions, drive an average of 37 miles a day. Forty-two percent of Multnomah County households spend more than 45 percent of their income on transportation plus housing. If per-household VMT in Dane County dropped to the level in Multnomah County, housing plus transportation costs would become affordable for many thousands of families currently struggling with those costs.
Conclusion
How much we drive is a function of the types of communities we live in. Creating more places to live in compact, mixed use, connected locations with many transportation options will reduce driving and enable us to meet our regional climate, opportunity, and conservation goals. Carrying out the Regional Development Framework’s growth strategies will reduce VMT, reduce household greenhouse gas emissions, and reduce combined costs of housing and transportation. A decline in per-household VMT will tell us that the region is making progress towards these goals.
Learn more and view our other performance indicators at rdf-carpc.hub.arcgis.com.