The main purpose “Slow Speed Neighbourhoods” is to create a safer and quieter street environment for all residents and road users. Slower speeds are expected to reduce the occurrence of crashes and their severity if they do occur. The OECD’s International Transport Forum Speed and Crash Risk report(external link) outlines the relationship between speed and crash occurrence and severity. It shows that if impact speed increases from 30 km/h to 40 km/h the risk of fatal injury to a pedestrian or cyclist is about doubled. Other internationally adopted research supports the recommendation that relatively small changes in speed can have a high impact on crash survival rates.