http://www.dft.gov.uk/stellent/groups/dft_roads/documents/page/dft_roads_029962-52.hcsp#P1957_189933
UK Advisory Group on Motorcycling: Final Report to Government
http://www.dft.gov.uk/stellent/groups/dft_rdsafety/documents/page/dft_rdsafety_030137.pdf
