Climate-Smart Transportation: Good for Cities and People

In a leafy Seattle neighborhood on the shores of Lake Washington, Nathaniel Henry, PhD, is explaining the 15-minute city concept by pointing exuberantly in all directions. 

“There’s a convenience store over there, restaurants here, a bakery a block over there, a school a block over there,” says Henry. “There’s a park and an elementary school. There’s the bus line that goes to downtown Seattle, and a small library over there.” 

The stroll along the Madrona neighborhood’s central shopping corridor vividly demonstrates how residents can easily walk, bike, or use public transit for most daily excursions in trips that typically don’t exceed 15 minutes—improving air quality and increasing their physical activity in the process. 

As he heads down a hill toward a grocery store, he notes “cool safety features” that encourage walking or cycling, like dedicated bike lanes and a pedestrian-only street during school drop-off hours.   

Henry, a 31-year-old data geography consultant who does not own a car, believes in the transformative power of walkable neighborhoods like Madrona for residents’ health as well as the environment’s. In April, he launched a tool that maps 15-minute neighborhoods nationwide called Close, which has already had 2 million pageviews.   

“People understand more now about carbon footprints,” he says. “Just because the suburbs look greener doesn’t mean they’re the green choice.” 

Indeed, transportation is the largest contributor to human-generated greenhouse gas (GHG) emissions in the U.S. At Johns Hopkins’ Center for Climate-Smart Transportation, researchers are exploring how the 15-minute city and other evidence-based approaches could help municipalities address such alarming issues and reshape how people travel. The Center, which is funded by the U.S. Department of Transportation and includes six institutions, has a key goal: Make climate change the center of every transportation decision.  

“It’s extremely important to think about how we can reduce these emissions and move toward meeting greenhouse gas emissions target reductions,” says Shima Hamidi, PhD, MSc, the Center’s director. “What actions and policies can help? It starts with cities.” 

Cities at the Forefront  

Researchers at the $10 million Center are investigating strategies that could make the transportation sector more environmentally friendly. While city-level climate action plans are widespread, the majority are falling short of their GHG emissions targets. 

“We want to know the reason: Why did they fail to come up with actionable plans and policies?” Hamidi says.  

The Center’s research can help city officials identify evidence-based approaches to meet their targets. For example, the Center’s 15-minute city project uses AI and anonymized data from millions of U.S. cell phones to better understand where people travel on a daily basis. Policymakers could use those findings to incentivize more commercial areas closer to neighborhoods, or to add public transit options along common driving routes.  

“If you really want to switch from driving to environmentally friendly options, you have to give people the option, and most often the option isn’t available,” Hamidi says.  

Findings from this research will be published in academic journals and shared in places like the upcoming World Health City Forum. That meeting, which will be held in South Korea in November, focuses on how cities can address challenges like climate change. The emphasis is urgent, says Seydina Fall, MBA, a senior lecturer at Johns Hopkins Carey Business School, who plans to attend the forum.  

“Cities have the most impact in changing daily lives,” he says. “We don’t have a choice but to change.”  

Making Climate Smart Options Accessible  

Many of the Center’s projects explore how changes to active transportation options like walking, biking, or public transit might increase adoption.  

A striking example is the successful promotion of cycling in Bogotá, Colombia, says Francisca Rojas, PhD, MCP, academic director at the Bloomberg Center for Public Innovation at Hopkins. In Bogotá, the combination of clogged city streets, a temperate climate, and an extensive network of protected bike paths makes biking an appealing alternative to sitting in traffic. Even so, the city faced a gender gap among cyclists. Many women, who are often caregivers of elderly relatives and children, had little time to learn how to ride a bike, encountered cultural norms that discouraged female cycling,  and didn’t feel safe on the roads. To change that, the city poured resources into community centers that could offer child care and bike education for women as part of their Care Blocks policy. They also invested in additional infrastructure to make cyclists feel safer.  

“Once there are bike lanes and barriers from traffic, women get on bikes,” Rojas says. “If that doesn’t exist, there’s a heightened risk perception for women.” 

The changes had a noticeable impact: Of all the trips women made in 2023, nearly 4% were on a bicycle, up from 1.6% in 2011, according to Bogotá’s travel survey. 

Physical comfort also influences people’s transportation choices, notes Alessandro Rigolon, PhD, an associate professor of City & Metropolitan Planning at the University of Utah, one of the institutions in the Center.  

“Cities are increasingly asking their residents to avoid driving to mitigate climate change,” he says. “But what are cities doing to adapt to climate change and create better conditions for active transportation?” 

While there are widespread efforts to make biking safer, there’s less emphasis on making it comfortable to bike or walk in hot weather. So, he’s exploring strategies like planting more trees along common cycling routes or alongside sidewalks where families might walk to school. Shelters or tree shade near transit stops might encourage people to wait for the bus, even on a scorching day. 

Morgan State University Professor Celeste Chavis, PhD, MS, also pays attention to the role of convenience through her work with the Center. If environmentally friendly options like public transit also reduce commute times, for example, people are more likely to choose them.  

“Everyone understands the link between transportation and climate change,” she says. “But you have to understand the way people feel: How long does it take me to get to work?” 

Likewise, when it comes to electric vehicles (EVs), finding a nearby charging station matters. It’s a major issue in cities like Baltimore, where few rowhomes have dedicated driveways that allow people to easily charge their vehicle.  

That prompted Chavis to map the city’s public EV chargers, monitor who is using those chargers, and survey current EV owners about where they charge. The ongoing project will examine whether existing public chargers in city parks and city-owned garages are serving city residents or outside commuters. The decision of where to place additional chargers may also depend on the city’s goals: Is it more important to encourage city residents to buy an EV or get more clean vehicles coming into the city?

Technology Offers Potential  

As cities grapple with climate-smart policies and their challenges, technology offers some helpful tools.  

At the University of Texas at Austin, another partner institution, Junfeng Jiao, PhD, is studying how a digital transportation model might guide sustainable transportation choices. This technology uses cameras to display traffic and commuter demand patterns in real time to help city planners create transit availability that better fits travelers’ shifting needs, such as adding extra buses during a particularly busy commute time. It could also predict how events like a major sports game downtown might impact public transit demand or identify if a certain transportation hub needs more shared bikes or scooters.  

“Many times, there’s a huge demand for public transit but there’s no train or bus going by,” he says. “If we can better meet demand and supply, we can significantly increase the usage of different transportation modes and reduce carbon dioxide emissions.” 

Jiao is also looking into the role of robots in reducing frequent, short consumer drives, such as running out to the grocery or drugstore. The pilot will test robotic delivery of soft drinks and other convenience store items from a central location on the UT campus.   

“Smart transportation and smart cities in our country are lagging behind … Europe or Asian countries,” he says. “I think there is a lot that can be done with our technology and our resources.”

Better Options, Better Choices  

Creating an environment that’s more conducive to active transport helps people make more climate-friendly choices, says Portland planning consultant Ben Schonberger, MCP. From his home, Schonberger can walk to a grocery store, a UPS store, and the elementary school his children attended. He bikes to work, using a route that has safety elements like speed bumps to slow down traffic and flexible posts at intersections that define the bike lane.  

“Is it not more fulfilling and enriching to be able to walk your kid to school without being terrified of getting run down, or to have a grocery store within walking and biking distance?” he says. “If you can do more outside, it’s not just good for the planet, it’s good for individuals in terms of their health and happiness and ability to thrive.”