The report, written by AECOM, found that there were 20 collisions in 2017 involving a trailer that resulted in injury or death where the trailer was a contributory factor. Looking at all collisions (not just those involving injury), it found that vehicle-related factors numbered 62; people-related numbered 358; road-related factors were 65, and other categories were assigned to 33.
The report concludes: “An in-depth study of road accidents suggests that trailer vehicle defects are not a major cause of injury incidents.”
However, that does not mean that light trailers were in good shape; according to DVSA statistics of roadside stops, about 50% of O2 trailers [750kg-3.5t gvw] checked were non-compliant. Tyre defects and hitching issues were most prevalent causes in the case of O2 trailers, citing data from breakdown services, trunk road monitoring and off-road studies.
For larger O3 and O4 trailers, 3.5-10t, and above 10t gvw, respectively, the compliance rate averaged 20%. As to the causes of the difference in condition between light and heavy trailers, which are already regulated as commercial vehicles, the report points to enforcement, operator licencing and annual testing.
The authors added that they were unable to determine which trailer types were involved injury accidents.
Light (O2) trailers are not currently required to be tested annually, but they must be tested after one year of entering operation.
The authors estimate that there are about 1.4m O2 trailers operating in the UK, about a third of which are caravans. In comparison, some 250,000 heavier trailers were tested for a mandatory MOT in the 2018-2019 period.