Licensed to skill: contributory factors in road accidents

Since 2005, official accident records have included additional information on contributory factors which are designed to provide insights into why and how road crashes happen and to help develop measures aimed at preventing them. A total of 77 categories of contributory factor are available. These provide information on the factors which the police officer attending the scene considers may have contributed to the cause of the accident. They are intended to identify the key actions and failures which led directly to the impact. This report looks at over 700,000 items of official crash data to pick out common themes.

Many of the issues which receive the most media coverage are not actually among the most common contributory factors. Speeding, drink driving, mobile phone use, tailgating, road rage and bad weather are all important but are not as frequently reported as driver errors.

The report shows the top 10 factors for different crash severities, driver age, road types and other issues such as weather and time of crash. These ‘top 10s’ show key variations which the IAM believe can be useful in the design of future interventions.

Accidents involving younger and older drivers show different contributory factors and these can be used to tailor training and assessment solutions. For example, ‘Learner or inexperienced’ is recorded as a contributory factor more frequently on rural roads, minor roads and 60 mph roads than elsewhere – confirming the IAM’s view that the driving test does little to prepare new drivers for the highest risk activities.