TRL’s research in Phase 1 of this project focussed on estimating the frequency of wheel fixing problems and identifying potential countermeasures to prevent or mitigate future problems. The project estimated there were between 7,500 and 11,000 cases of loose wheel nuts and between 150 and 400 wheel detachments resulting in 10 to 27 injury accidents and 3-7 fatal accidents each year in the UK.
This second phase of the project was again commissioned by the UK Department for Transport (DfT) and has built upon the 2006 research by TRL in order to identify best practice for wheel tightening and maintenance, and to assess the potential effectiveness of identified countermeasures.
This is the final project report for Phase 2 of the project. It describes the methodologies and results from the tests the second phase of the project including a mathematical analysis of the clamp force required during normal driving, laboratory, vehicle-based tests to investigate various procedures for initial tightening and re-torquing, and accelerated wear tests were also completed to assess the effectiveness of the various countermeasures.

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