No proof speed caused accidents

Apparently, ambulance dispatches for traffic accidents rose across the province by 11 per cent in the six months after the increased speed limits. The cause for that wasn’t the increased speed limits: they affected only a small fraction of our roads.

The other two studies quoted by the authors indicate that accidents, injuries and deaths on the roads that did have increased speed limits went up by a roughly similar amount as the province as a whole. Based on that, how could they conclude that the increased speed limits caused increased accidents? Ian Miller, Tsawwassen