After a collision between a pedestrian and bus, a UK road authority reviewed vehicle speeds.
A curve in the road obscured the pedestrian crossing on approach. After reviewing vehicle speeds on the Compass platform, the authority found that only 2% of cars were travelling at 25-31mph, above the 30mph speed limit on the bend and through the junction. All other vehicles were travelling at speeds below the posted speed limit.
Since most cars were travelling under 20mph in the 30mph zone, speed was likely not a factor. However, g-force data showed last-minute harsh braking events (above -0.2g) occurred at low speeds and more often after 5pm.
Literature suggests that anything above -0.3g is a harsh braking event. Other case studies by the Road Safety Foundation propose safe thresholds should be lowered to -0.2g, particularly around pedestrian crossings or high traffic areas, meaning that traffic context is an important factor.
On approach to the pedestrian crossing g-forces were above -0.2g, exceeding -0.3g, despite cars travelling at a low speed of 20mph. This suggests visibility and lighting issues rather than speeding or driver error.
While near-misses show where drivers are losing friction with the road, they can further be complemented with harsh braking events to identify crash risk hotspots.