As more U.S. cities embrace the Vision Zero approach to curtailing traffic and ensuring pedestrian safety, there’s plenty of compelling data in favor of slow roads coming out of Edinburgh, Scotland. The numbers show how lower speed limits can change drivers’ attitudes about bicyclists — and even let city-dwellers breathe a bit easier thanks to air quality improvement.

The easy-to-love capital city is rolling out a plan to cap the speed limit at 20 mph across 80 percent of its roads, including the entirety of its dense downtown. Key arterial roads will retain their speeds of 30 and 40 mph. After three years of planning, public engagement and pilot projects, as well as advocacy by Living Streets and 20’s Plenty For Us, the new strategy is explicitly about encouraging people to bike or walk, rather than drive.

Crucial details about cost and enforcement will come in an implementation report that is due in March. But what is certain is that change will begin to be phased in later this year. It is expected to be complete by the end of the 2017/18 fiscal year.

The last sweeping change in Scotland’s speed policy dates back more than 80 years, when it adopted 30 mph as its limit in 1934; before then, there were no restrictions on driving speed. At the time, there were about 2.5 million cars on British roads. Today, there are 31.5 million. The greater traffic density calls for a new road strategy. Between 2009 and 2013, there was an average of 2,842 bike and pedestrian casualties in Edinburgh, or about 22 percent of the Scottish total. Traveling at excess speed caused 13 percent of all reported accidents, and 20 percent of fatal ones. While the risk of fatal injury for pedestrians is only 1 percent when the vehicle is traveling at 20 mph, it jumps up to over 30 percent when the speed is 40 mph.

Slow roads are a meaningful intervention here. Down south, Portsmouth became the first city in England to put 20 mph limits in place over most of its streets, and even though it didn’t include traffic calming features as part of the plan, it still saw a drop in accidents and casualties. Pilot projects in Edinburgh revealed that the number of people who believed cycling to be unsafe fell from 26 percent to 18 percent. The number of young children riding bikes to school tripled, while, among older kids, the rate of bike-riding to school went from 3 percent to 22 percent.

Scotland’s council of Fife, which is home to St. Andrew’s, stands out as a slow roads pioneer. In 2003, its leadership adopted a 20 mph initiative that eventually encompassed nearly all urban residential streets. Ten years after the fact, an evaluation of the program is pending, but early indicators suggest that the policy had a tangible impact — traffic has indeed slowed — and there is “generally a very good level of support” for it, although few are fans of speed cushions or bumps.

Easing down the rush of traffic neatly connects to the newly energized effort to clean up air pollution in Scotland. Even as the country has steadily reduced emissions since 1990, it still has a tendency to break European air quality standards. Environmental groups connect this to serious public health problems that cost the National Health Service £2 billion annually. In January, Scotland adopted a low emission strategy for sustainable growth and an increased quality of life.

Emilia Hanna, the air pollution campaigner for Friends of the Earth Scotland, told the BBC that traffic fumes in urban areas are a leading cause of poor air quality, meaning that the new speed restrictions can be part of a larger evolution. “One of the biggest barriers to walking and cycling is fear of speeding traffic, so 20 mph zones, if accompanied by greater investment in active travel infrastructure, could transform how people move around the city,” she said. Importantly, the “good practice guide” developed for Edinburgh by Transport Scotland points to how pollution has a disproportionate effect on disadvantaged communities, suggesting that slower traffic can reduce health inequities.

Edinburgh’s move also syncs with the Scottish government’s 2010 Cycling Action Plan, which aimed for 10 percent of all journeys to be taken by bike by 2020. When the plan was updated in 2013, urban areas were encouraged to introduce more 20 mph streets.

The city’s pro-active shift to slow roads is inspiring its neighbors. Residents of Glasgow, Scotland’s most populous city, have recently committed to capping speeds at 20 mph for all residential roads, but residents are petitioning their council to expand the policy to commercial districts. “These lower speeds encourage more considerate driving, leading to safer streets for pedestrians, cyclists and motorists,” they argue. Likewise, a councilor in Dundee is introducing a 20 mph proposal, suggesting that Edinburgh’s best practices can also work for the nation’s fourth largest city. And speed cameras are looking like they will become more popular across the board in Scotland, bringing greater awareness and transparency to road safety.

One important point that Transport Scotland makes in its slow roads report is that reducing speed limits are not a shortcut to “complete streets.” “They should not be set in isolation, but should be considered as part of a range of other measures to manage speeds, improve safety and meet other objectives, including the encouragement of active travel,” it says.

Enforcement is, of course, an immediately pressing point. Not everybody is happy about the pending slowdown in Edinburgh. A procession of black taxi cabs demonstrated recently, pointedly trying to bring traffic to a standstill. Drivers are concerned that the slow road plan will backfire, causing more rather than less congestion, disinclining people to take taxis.

The city council’s transport convener, Lesley Hinds, has said before that she understands that public consultation at each step is essential in moving toward “a culture change in the capital.” To make the 20 mph speed limit workable, and not just a philosophical point, the council plans to focus on signage and road paint, as well as calming measures like pedestrian islands. Speed bumps will not be used on any main streets served by the bus system.

The most recent public poll of Edinburgh residents showed that 60 percent supported the 20 mph limit. And much of the opposition is fueled by misconceptions, including the concern that it will be a blanket rollout or that it will hurt commercial districts.

For his part, Stuart Hay, head of Living Streets, has his eye on the prize. “If this encourages more people to be active, it could have the biggest impact on public health since the smoking ban,” he wrote in The Scotsman.