Our Driving Habits Must Be Part of the Climate Conversation
As the United States grapples with meaningful action on climate change, much emphasis has been placed on the transportation sector, and with good reason. Transportation accounts for 29 percent of the country’s greenhouse gas emissions, the most of any sector. A majority of these emissions, unsurprisingly, come from passenger vehicles. Americans’ reliance on personal vehicles helps rack up a staggering three trillion vehicle miles traveled (VMT) each year, totaling over 14,000 miles for each licensed driver.
This is not merely personal preference; many residents have little choice but to drive in order to reach everyday destinations such as offices, grocery stores, retail centers, and schools on account of sprawling land use patterns.
Beyond the climate consequences resulting from transportation emissions, this high baseline of driving has given rise to a range of societal ills in American cities. These include inequitable access to destinations, disconnected communities, and the nearly universal frustration of congestion. Our highway system has served to segregate populations, heightening long-standing injustices, while high costs of living and limited housing options continue to facilitate sprawl away from city centers.
As citizens contend with long commutes and frequent traffic jams in their daily trips, VMT figures continue to rise and place additional strain on the transportation system. To compound all of these issues, the nation’s infrastructure has been in a state of general disrepair for decades.
The Need to Reduce VMT
To avoid perpetuating the unsustainable “business-as-usual” approach to transportation in this country, elected officials and transportation professionals must start seriously considering strategies that can reduce the amount of driving that takes place to begin with. RMI analysis indicates that the United States must reduce VMT by 20 percent before the end of the decade to limit warming to 1.5°C—and this remains true even under ambitious EV adoption scenarios.
Accomplishing this and other lofty climate goals requires elevating the importance of land use and transportation policies to help reduce overall vehicle travel. This is an especially timely consideration as Congress continues a pivotal deliberation over the future of the nation’s infrastructure.
Significantly reducing VMT on a national scale will be no small feat, considering the sprawl that has been deeply baked into our cities and highways over the past century and our shared cultural norms surrounding driving. Admittedly, individual citizens often have little agency to combat this car-dominated model of transportation.
Fortunately, at the systemic level, policymakers and city planners do have a number of powerful tools in their arsenal to combat high VMT figures, should they choose to prioritize the issue. Several key interventions, from reforming harmful land use practices to implementing novel policy incentives in the transportation space, demonstrate potential to deliver impact quickly in this decisive decade for climate action.
Interventions to Reduce VMT
In many ways, solving the issue of high VMT begins with land use. Many vehicle trips originate from the simple fact that where people live rarely coincides with where they work, shop, and recreate. Smart growth development strategies can help remedy this disconnect by co-locating residential density with popular destinations. Infill development and transit-oriented development (TOD) promote more compact, walkable urban communities available for everyone’s use. They can also prevent new projects from being pushed to the urban fringe, where it’s difficult to reach key destinations without driving.
Relaxing restrictive city rules can also promote the kind of vibrant communities that claim top dollar for commercial and residential properties. This does not jeopardize anybody’s right to live in a single-family detached home, for those who prefer to do so; rather, it provides alternatives that can bolster “missing middle” and multifamily housing in American cities. Smart growth alone could bring down VMT by an estimated 5 to 20 percent while helping to improve convenience, access, and equity.
A variety of pricing signals in transportation policy may also incentivize behavioral change that reduces overall driving. Congestion pricing and parking pricing schemes can persuade drivers to consider alternative forms of transit and alleviate rush hour traffic jams. Pay-as-you-drive (PAYD) policies could introduce scalable registration, insurance, or road usage charges based on mileage driven.
Such policies do raise equity considerations that must be considered prior to implementation. However, it’s important to reiterate the inequity of the present system. Transportation investments overwhelmingly favor the personal vehicle over public transit and other non-drivers despite the oversized environmental and social costs associated with driving.
Further, because the federal government uses tax dollars to fund transportation, non-drivers are essentially subsidizing drivers. In most cases, thoughtful reforms would improve upon the status quo. Pricing signals could reasonably reduce VMT by 5 to 15 percent, depending on their design.
Somewhere in between land use and transportation policy lies the matter of reforming roadways themselves. Stopping highway expansions can help curb increases in VMT. Research demonstrates that highway lane buildouts, historically exploited to combat congestion, actually tend to increase driving through “induced demand” and lose their decongestion benefits in a matter of months to several years. Planned highway expansions in Colorado, for example, would increase statewide VMT by as much as 3 percent by 2030.
Street redesign emphasizes the reallocation of road space away from private vehicles to develop “complete streets” that promote safe bus, bike, and foot traffic. Relatedly, improving the connectivity of roadways (a gridded network, like most downtowns have) can allow for more efficient travel routes than meandering roadways and cul-de-sacs. Enhancing street space allocation and road connectivity could yield 3 to 6 percent reductions in VMT.
A Path Forward on Reducing Driving
While each of these interventions might help reduce VMT independently, their benefits will compound if integrated together under a comprehensive transportation demand management (TDM) plan. Broadly, TDM aims to provide travelers with more effective, reliable alternatives to driving, including many of the aforementioned strategies.
Additionally, it can involve a variety of measures from direct investments in public transportation to employer-driven measures like carpooling initiatives and hybrid work models. Seattle has been particularly successful with its integrated TDM plan, with 75 percent of people traveling in non-single occupancy vehicles despite population growth.
Implementing effective land use and transportation measures is often easier said than done, of course, as a range of barriers impede their feasibility. Some of the more rigid obstacles exist in the form of exclusionary zoning codes, minimum lot sizes/setbacks, parking requirements, and other restrictive measures that tend to facilitate sprawl. Several less tangible, but equally problematic, barriers include the contentious political climate, opposition to development from neighborhood coalitions, and special interest groups that benefit from the existing system.
Overcoming these obstacles will require concerted leadership and coordination among stakeholders across the nexus of land use and transportation, but the consequences of continuing with business as usual are too dire to not correct our course.
At present, the United States possesses the means, if not the momentum, to cut back on overinflated transportation emissions through land use and transportation reform. As states and localities plan for sustainability in the coming decades, greater emphasis must be placed on strategies that can reduce vehicle miles traveled. While the personal vehicle is not going to disappear overnight, thoughtful interventions can afford people the option to eschew driving as it becomes easier to walk, bike, or ride public transit to more of their everyday destinations.
By shifting the scales of convenience toward modes of transportation other than driving, we can simultaneously meet the demands of the climate crisis and improve quality of life.
The authors of this blog are CU Boulder graduate students working with the Urban Transformation team on a capstone project. Later this year, the CU Boulder capstone team and RMI will be releasing additional thought leadership on a series of potential land use and policy reform interventions to help reduce driving in the United States.
Acknowledgment: We thank Ben Holland of the Urban Transformation team for his contributions to this article.