AUSTIN — Domingo Martinez, 42, was crossing East Riverside Drive when a vehicle struck and killed him on Nov. 8. Police said the driver did not stop to provide aid.

Bethany Clark, 20, was crossing Howard Lane when a city bus fatally collided with her as it made a right turn on Sept. 14.

And an unidentified man in his 30s died trying to cross Interstate 35 in South Austin when an 18-wheeler hit him on Sept. 22.

These are only a few deaths caused by vehicle crashes in a record-breaking year for Austin, which has seen more than 90 people killed on city streets so far in 2015 — up from 63 last year. Statewide, Texas had more than 3,000 fatal car crashes in 2013, the most recent year for which detailed data are available. That's more than any other state.

Public health experts warn that a lack of safety on Texas roads is not just killing thousands of people each year. It's taking an even greater — if less visible — toll on life expectancy. That’s because a lack of safe options for pedestrians and cyclists is discouraging Texans from being more active, they argue, at a time when the state is suffering from historic rates of obesity.

“People didn’t always used to make the link between transportation and how that affects health, and how zoning affects health, but they are so key,” said Phil Huang, medical director for Austin's Health and Human Services Department. “The built environment, the environment we live in, plays a huge role in our health.”

Reducing car crash fatalities is one obvious goal, “but when we look from the health standpoint, the inactivity is actually more important than the fatalities overall” because of the effects of conditions like heart disease and diabetes, said Jay Maddock, dean of the Texas A&M School of Public Health, which is studying how neighborhood design in Austin can affect the health of the people living there.

“For us, it’s really about getting people moving, and then trying to do so in a way that safety’s not a concern,” he said.

For researchers, one worrisome trend for public health in the United States is the sharp drop in the number of kids who walk or bike to school. Nationwide, nearly half of kids did so in 1969, according to the advocacy group Safe Routes to School. Today, that number is around 13 percent.

The effect has been dramatic, said Stephen Pont, a pediatrician at Dell Children’s Hospital in Austin who studies childhood obesity.

“This obesity crisis is going to very realistically threaten the American dream,” he said. “Our kids are not going to live as long as we are.”

Pont said physical activity is not a “silver bullet” for the obesity epidemic, and he said policymakers should also prioritize goals like reducing the number of sugary drinks kids consume. But he said public school officials can meaningfully improve children's health by advocating for safer walking and biking routes to school.

“We all have cars and we drive way more than we used to; we have jobs that are sedentary,” Pont said. Changing those behaviors “can be difficult,” he said, “but that doesn’t mean it’s not worth doing.”

In Houston, the city is partnering with researchers from the school of public health at the University of Texas Health Science Center at Houston to identify social factors that put people at risk for diabetes.

Researcher Stephen Linder said he surveyed Houstonians in three different neighborhoods that varied demographically and socioeconomically but were all considered vulnerable to diabetes. At-risk residents in those communities shared commonalities like feeling “disconnected” from their neighborhoods, which they said lacked amenities like sidewalks and bike lanes, according to Linder. Other people felt pressed for time to exercise in part because they had long driving commutes to work, he said.

Faith Foreman, assistant director of the Houston health department, said the findings validated the city's work to make physical activity a “major priority.” But Houston has a tough road ahead. Only about 3 percent of Houstonians walk or bike to work, according to U.S. Census data.

Foreman spoke by phone from Copenhagen, where she and Linder were presenting their findings on the diabetes study. “Everyone here rides a bike,” she said of the European city. “But cities have to be designed for you to do that.”

For local governments in Texas, these questions of how to improve public health become more urgent by the day. According to projections from the state demographer, Texas’ diabetic population will quadruple by 2040. A September “call to action” from the U.S. Surgeon General put pressure on cities to play an active in improving health by encouraging walking.

But public health researchers admit the implementation of those policies is proving difficult. The Austin City Council in 2014 endorsed a “Vision Zero” goal to completely eliminate road deaths. With more than 90 fatalities so far this year, the city is farther from that goal than ever before.

For Eileen Nehme, a public health consultant and member of Austin’s Vision Zero advocacy group, improving walkability often requires cities to make changes like allowing denser forms of housing, reducing driving speeds and making investments in infrastructure — which can meet fierce political resistance.

“This is the part that’s hard to say, and people don’t normally want to say it, but we’re going to have to be a little bit uncomfortable,” she said. “People are going to have change their habits.”

Disclosure: Texas A&M University is a corporate sponsor of The Texas Tribune. A complete list of Tribune donors and sponsors can be viewed here.