An increasing proportion of new vehicles are being fitted with autonomous emergency braking systems. It is difficult for consumers to judge the effectiveness of these safety systems for individual models unless their performance is evaluated through track testing under controlled conditions. This paper aimed to contribute to the development of relevant test conditions by describing typical circumstances of pedestrian accidents. Cluster analysis was applied to two large British databases and both highlighted an urban scenario in daylight and fine weather where a small pedestrian walks across the road, especially from the near kerb, in clear view of a driver who is travelling straight ahead. For each dataset a main test configuration was defined to represent the conditions of the most common accident scenario along with test variations to reflect the characteristics of less common accident scenarios. Some of the variations pertaining to less common accident circumstances or to a minority of casualties in these scenarios were proposed as optional or supplementary test elements for an outstanding performance rating. Many considerations are incorporated into the final design and implementation of an actual testing regime, such as cost and the state of development of technology; only the representation of accident data lay within the scope of this paper. It would be desirable to ascertain the wider representativeness of the results by analysing accident data from other countries in a similar manner.

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The aim of this study was to describe the position of pedestrians and pedal cyclists relative to the striking vehicle in the 3 s before impact. This information is essential for the development of effective autonomous emergency braking systems and relevant test conditions for consumer ratings. The UK RAIDS-OTS study provided 175 pedestrian and 127 pedal-cycle cases based on in-depth, at-scene investigations of a representative sample of accidents in 2000-2010. Pedal cyclists were scattered laterally more widely than pedestrians (90% of cyclists within around ±80° compared to ±20° for pedestrians), however their distance from the striking vehicle in the seconds before impact was no greater (90% of cyclists within 42 m at 3 s compared to 50 m for pedestrians). This data is consistent with a greater involvement of slow moving vehicles in cycle accidents. The implication of the results is that AEB systems for cyclists require almost complete 180° side-to-side vision but do not need a longer distance range than for pedestrians.

The potential effectiveness of vehicle-based secondary safety systems for the protection of pedestrians and pedal cyclists is related to the proportion of cases where injury arises by contact with the road or ground rather than with the striking vehicle. A detailed case review of 205 accidents from the UK On-the-Spot study involving vulnerable road users with head injuries or impacts indicated that contact with the road was responsible in 110 cases. The vehicle however was associated with a majority of more serious casualties: 31 (vehicle) compared with 26 (road) at AIS 2+ head injury level and 20 (vehicle) compared with 13 (road) at AIS 3+ level. Further analysis using a multivariate classification model identified several factors that correlated with the source of injury, namely the type of interaction between the striking vehicle and vulnerable road user, the age of the vulnerable road user and the nature of injury.