JUST BAN THEM:

In July 2016, the city of Edinburgh implemented a bold change. It lowered the speed limit on almost all of its roads from 30 mph to 20 mph that didn't already have a 20 mph speed limit. The city center, main streets, and residential roads all became 20 mph zones. The only roads that retained 30 or 40 mph speed limits were in the city suburbs. 

At the same time, a group of researchers, including ones at the University of Edinburgh, formed a team called "Is Twenty Plenty For Health?" to study the impacts of the new 20 mph policy. The results all pointed in one direction: 20 mph is plenty. The zones with a reduced speed limit saw 371 fewer crashes per year, or 38 percent, including fewer crashes involving cyclists and pedestrians. On average, cars went slower. And, as a rule, people felt safer biking and walking. These results have been replicated in further studies since and most of London is now a 20 mph zone, too.

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