“To combat climate change and to reduce emissions and reduce driving, you have to take action at all different levels of government,” Northeastern professor Serena Alexander explains
It’s an environmentalist’s adage: think globally, act locally.
But does this strategy work for reducing greenhouse gas emissions produced by vehicles?
New research from Northeastern University finds that it’s a mixed bag.
“Overall, climate planning strategies help us reduce driving or help us increase non-auto commutes,” says Serena Alexander, associate professor of public policy and environmental engineering at Northeastern. “But certain strategies work a lot better at the local level and, for other strategies, regional alignment is important.”
Transportation accounts for the largest portion of greenhouse gas emissions in the United States, with 28% of greenhouse gas emissions attributed to the sector. Fifty-seven percent of those emissions are from passenger or light-duty vehicles, according to the Environmental Protection Agency.
But vehicle miles traveled — a measure of how much Americans drive — continues to rise, even despite the growth of remote work during and after the pandemic.
“We have struggled tremendously in reducing emissions from transportation,” Alexander says. “The main reason being that we have struggled in reducing driving even in places where we have done a lot of climate planning.”
The state of California exemplifies one of those places.
In 2008, the state passed the Sustainable Communities and Climate Protection Act, which aims to reduce greenhouse gas emissions through coordinated transportation, housing and land use planning.
The act set regional targets for reductions in greenhouse gas emissions from passenger vehicles, and regional metropolitan planning organizations worked with municipalities to devise strategies to meet these reductions.
For example, to reduce emissions by a certain amount, the region may adopt strategies like improving public transit, creating more bike path networks or streets that can be dedicated to multiple uses rather than just cars, or building more housing near transit stops, etc.
At the end of the day, however, Alexander notes that it is the local municipality that actually implements most of the strategies — planting the street trees or maintaining the bike path, for instance, or rezoning neighborhoods.
“To combat climate change and to reduce emissions and reduce driving, you have to take action at all different levels of government,” Alexander explains. “So, how do we make sure that these different levels of government work together in an effective, efficient way?”
To find out, Alexander received funding from the Mineta Transportation Institute to lead a team that evaluated 25 California cities and several climate planning strategies in four areas: improving transportation infrastructure; zoning and planning strategies; reducing vehicle demand; and overarching or integrative strategies (for example, green infrastructure and renewable energy initiatives).
The results, published in the journal Sustainability, as well as in a report, find that, as Alexander says, “planning matters.”
Just having climate planning strategies resulted in a nearly 20% increase, on average, in non-auto commutes, according to the research.
But Alexander found certain strategies were most effective if implemented at the local level. These include community engagement, community education, parking requirements, urban forestry, even managing freight delivery and “last mile” delivery — or the final step in getting something delivered to your home.
On the other hand, mass transit and “complete streets” — or streets designed for multiple uses rather than solely automobiles — were most effective if regionally coordinated. Open space and preserving critical environments were also most effective when addressed regionally.
In terms of impacts, well-aligned regional and local climate friendly infrastructure such as energy-efficient lighting and increasing tree canopies led to a 7% reduction in driving trips as it encouraged walking. Aligning strong transit access with housing and jobs was also effective in reducing driving, as did density, walkability, diversity and strong transit systems.
But Alexander notes that “a lack of alignment does not mean a lack of action.”
The research found climate planning strategies were much more aligned in the Bay Area than in the area of southern California governed by the Southern California Association of Governments (SCAG). She hypothesizes it is due to the population patterns in each region. While SCAG is dominated by the sprawling Los Angeles region, Alexander notes that the Bay Area has three competing cities with large populations: San Francisco, Oakland and San Jose.
“When Los Angeles developed its plan, they likely prioritized local needs, leading to a unique approach that diverged from broader regional efforts in the nation’s largest metro area,” Alexander says. “It’s not necessarily a bad sign, it just means that patterns of climate planning across the state and across the nation vary in terms of how different jurisdictions do things.”
“There’s no one-size-fits-all approach here,” Alexander continues. “Every jurisdiction needs to find out what it is that works for them within their specific context.”