Researchers are standing by evidence suggesting that 20 mph (32 km/h) roads improve road safety despite new figures showing casualties have increased substantially.

Data from the Department for Transport show that 2262 people were injured in 2011 on roads in built up areas with 20 mph speed restrictions—up 24% from 2010.1

Most of these—1966 people—had slight injuries, while the number of deaths—seven—was a 17% increase on the previous year. There were 289 serious injuries in 2011, up 39% on 2010.

The figures have intrigued researchers who have studied 20 mph roads and say they prevent casualties.

Chris Grundy, lecturer in geographical information systems at the London School of Hygiene and Tropical Medicine …