Roadside safety barriers are designed to deflect errant vehicles back onto the carriageway, preventing them from encountering potentially dangerous off-road hazards or from crossing into the opposing carriageway on dual carriageways. However, in recent years there is a perception that the numbers of so-called Sports Utility Vehicles (SUVs) and of Multi-Purpose Vehicles (MPVs) on UK roads has increased significantly, and there are concerns that these vehicles, by virtue of their greater mass and height, may not be well catered for by the current design of safety barrier, which is tested to withstand an impact with a 1500kg standard car only. Motor caravans also give cause for concern in this respect.
This report describes a simple criterion which could be used to differentiate between SUVs, MPVs and motor caravans on the one hand, and standard cars on the other. The perceived increase in numbers of SUVs and MPVs on UK roads is also confirmed to be real.
An analysis of UK National accident statistics is presented, which indicates that the occupants of these larger vehicles generally incur less severe injuries than occupants of standard cars, though this may well change as the growth in numbers of SUVs and MPVs changes the composition of the vehicle fleet. Only a small proportion of road accidents involve barrier strikes, and the involvement of a barrier is associated with increased likelihood of rollover and increased injury severity for occupants of all vehicle types. However, the increases in rollover incidence and in injury severity are found to affect SUVs and MPVs to a much greater extent than standard cars.
Detailed information on a small number of barrier strike accidents involving SUVs or MPVs taken from TRL’s specialised accident databases and from police accident reports held at TRL indicate that the barriers themselves are unlikely to be responsible for the observed increase in injury severity. The barriers are found to exceed their design specification in a number of cases, and the cause of the accident is found in several cases to be difficulty in controlling these larger vehicles in extreme situations. Speed and height of vehicle are found to be the best predictors of rollover incidence from the small number of cases where sufficient detail is available.

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