They were rolled out across Britain to cut speeds and prevent traffic accidents in built-up areas. But new figures suggest that the vast majority of drivers are speeding along many stretches of roads with 20 mph limits. According to the Department for Transport, three-quarters of drivers exceed the limit on “free-flowing” sections of 20-mph roads in England — those with no cameras, sharp bends, junctions or traffic calming measures. Half of drivers who admitted to speeding and were spoken to by the RAC said they sped on such roads because they felt the limit was “inappropriate” — a view also...