The biggest problem with UK limits is when they reduce a limit for an unrepresentative peak in accidents. When the figures regress to mean next year or two it'

The biggest problem with UK limits is when they reduce a limit for an unrepresentative peak in accidents. When the figures regress to mean next year or two it's taken as proof the new limit was correct. So we slowly deviate from the 85th percentile rule, and get weird stretches of dual carriageway at 30 or 40 with a speed camera in the middle.