In Montgomery County, where more people are killed in road accidents than in homicides, planners recently asked residents to tweet about their experiences as pedestrians.

They responded with photos of four-lane thoroughfares lacking sidewalks, bus stops with no nearby crosswalks, traffic whizzing past without buffers, and narrow sidewalks that end abruptly or are blocked by utility poles and overgrown bushes.

The problems, planners say, will be addressed in Montgomery’s first-ever pedestrian master plan aimed at making walking safer and more appealing in a Washington suburb where the car has long been king.

“We’ve had highway plans for 60 to 70 years,” said Montgomery planner David Anspacher. “This is the first time we’re doing a pedestrian master plan, and it shows. The pedestrian conditions aren’t great in Montgomery County.”

Montgomery, in Maryland, is among a growing number of car-centric suburbs across the country that are sharpening their focus on walking and cycling as a way to try to contain traffic congestion. They’re also responding to sweeping demographic changes, including more low-income residents and aging baby boomers, that have left more transit-dependent residents walking or riding to bus stops and rail stations. More suburbanites also want car-free commutes and a smaller carbon footprint, planners and public officials say.

“You have a whole lot more people walking along roads designed for suburban traffic,” said Bob Dallas, an Atlanta-area transportation safety advocate.

Meanwhile, more pedestrians and cyclists are dying. Nationwide, overall traffic fatalities declined in 2018, for the second-straight year, but the number of pedestrians and cyclists killed was up by 3.4 percent and 6.3 percent, respectively, according to the National Highway Traffic Safety Administration.

And a study by the Governors Highway Safety Association found that pedestrian fatalities nationally were recently projected to approach a 30-year high.

Governments in the Washington suburbs and in sprawling auto-oriented cities including Tempe, Ariz., and Charlotte are beginning to adopt Vision Zero, a traffic-safety strategy previously limited mostly to dense urban areas, such as the District, New York and San Francisco. In addition to Montgomery, recent suburban adopters in the Washington region include Prince George’s and Arlington counties and the city of Alexandria.

Many are wrestling with a central tenet of Vision Zero: Redesigning roads to lower speeds and reduce the severity of crashes. Planners and traffic engineers are narrowing lanes, lowering speed limits, adding crosswalks and making crossings more visible with brighter paint or flashing lights. They’re also separating vehicles and people via more-protected bike lanes and wider medians for pedestrians who can get only halfway across the road before the pedestrian lights turn red.

But undoing decades of auto-centric planning is proving a tall order. Many suburbs lack older cities’ wide sidewalks, tight street grids that provide frequent crossings, and narrower roads intended for lower speeds. Instead, many suburbs have four- and six-lane roads designed to move the most traffic as quickly as possible — and large numbers of motorists stuck in stifling congestion who say the last thing they need is lower speeds.

In Montgomery, for example, four people who were walking or were on bikes were killed from 2015 to 2018 in a four-mile stretch of Veirs Mill Road in the Rockville and Wheaton areas of Maryland outside the District. The speed limit is 40 to 45 mph, and, in some stretches, pedestrians have to walk as long as 15 minutes to reach a crosswalk, planners say.

“You have this kind of wide-open road that encourages you to speed up,” Montgomery planner Jessica McVary said.

In Tempe, a suburb of sprawling car-centric Phoenix and home to thousands of cyclists and walkers at Arizona State University’s flagship campus, officials are exploring lowering speed limits by 5 mph on streets four to six lanes wide. Doing so would give drivers more time to react and lessen the force of impact if a motor vehicle hits a cyclist or pedestrian, said Julian Dresang, Tempe’s city engineer.

“How you design streets can dictate how people use streets,” Dresang said. “That’s something we’re struggling with.”

Traffic engineers are quick to point out that motorists can make up much of the time lost to lower speed limits if traffic signals are timed to help them avoid red lights. Even so, attempts to lower speeds and implement “road diets” to protect cyclists and walkers have been controversial.

In Alexandria, opponents of a plan to add bike lanes to Seminary Road by shrinking the vehicle lanes essentially from four to two threatened to vote out members of the city council who supported the idea. While some residents said they needed safer cycling routes, others said such a “road diet” would make traffic worse and encourage frustrated motorists to cut through neighborhoods. The council narrowly passed the plan, 4 to 3, in September.

As Dresang said of public pushback, “Trying to change [car] culture isn’t always easy.”

In Charlotte, city officials implemented Vision Zero this year after traffic fatalities jumped 35 percent between 2016 and 2017.

Four in 10 road fatalities were related to speeding, and many of those occurred on four-lane roads with no dividers, said Angela Berry, the traffic safety program manager for the Charlotte Department of Transportation.

“We’ve committed to not creating those street types anymore,” Berry said.

Experts say most suburban jurisdictions are too new to Vision Zero to show how well, or whether, the approach can work on their vast road networks. Even some of the first large cities to adopt Vision Zero, including New York, San Francisco and the District, have seen mixed results.

But Leah Shahum, the founder of the Vision Zero Network, said the benefit of reducing speeds “is just a matter of physics.”

A pedestrian struck by a vehicle traveling at 20 mph has an 80-90 percent chance of surviving, Shahum said. If the vehicle is traveling at 40 mph, the pedestrian’s chance of survival plummets to 10-20 percent.

Suburban planners and engineers also are digging more deeply into crash data to pinpoint “high-injury networks” of roads. Many then prioritize those roads for repaving, which allows them to paint narrower travel lanes and new bike lanes.

While Arlington County officials are still drafting a Vision Zero plan, they’re looking at crashes through a “systemic lens” to spot possible road design problems that could be corrected elsewhere, Arlington planner Christine Sherman said.

“It makes your approach more proactive,” Sherman said. “We don’t have to wait for a crash to happen before we do something.”

Advocates of Vision Zero point to the success of Fremont, Calif., where wide roads designed for higher speeds reflect its growth during the 1950s. The city implemented Vision Zero in 2015, and traffic fatalities and serious injuries fell by 50 percent, from 36 in 2015 to 17 last year, officials said.

Matt Bomberg, a senior transportation engineer for Fremont, said the city added bike lanes, painted crosswalks with higher-visibility stripes and installed flashing crosswalk beacons. Repaved roads get re-striped with 10-foot-wide lanes, down from 12 to 14 feet wide. After the city replaced its street lighting, nighttime crashes dropped by 23 percent, he said.

Bomberg said the city also started focusing on the high-speed arterial roads where the “vast majority” of its most serious crashes occur.

“We started connecting the dots and found that 10 percent of our road network had 90 percent of the fatalities and 57 percent of the serious injuries,” Bomberg said.

Some safety advocates say that even with Vision Zero, improvements are taking too long. In Montgomery, critics point to two children recently being hit four months apart on Old Georgetown Road in Bethesda.

In July, 17-year-old Jacob Cassell was fatally struck by an SUV when he fell from his bike after possibly swerving to avoid trash cans on the sidewalk, according to published reports. In mid-November, a 13-year-old girl was seriously injured while riding in a crosswalk at the road’s entrance ramp to the inner loop of the Capital Beltway.

The executive director of the Washington Area Bicyclist Association, Greg Billing, said the region needs far more protected bike lanes. But he said he has also sensed that public officials in Montgomery and other D.C. suburbs have “stiffened” against the idea that motorists should take precedence on area roads.

Public officials “are really listening and helping communities organize and demand action,” he said.

Amy Ginsburg, the executive director of Friends of White Flint, said she was frustrated that it took more than nine months for the Maryland State Highway Administration to recently repaint crosswalks in the North Bethesda area. She said Rockville Pike still needs bike lanes and other improvements if the area is to continue transforming from auto-centric sprawl into a denser, more walkable and bikeable community.

Still, Ginsburg said, transportation agencies that once seemed intent on moving motor traffic are paying closer attention to protecting all road users.

“I truly believe there’s been a sea change in thinking,” Ginsburg said. “Everyone is realizing people want to get out of their cars. Now it’s just a matter of undoing 50 years of car-centric planning to make that a reality.”