Human factor, you don't say where you got your 7% figure from but, in a HofC committee report, published June 2002, the DTLR stated that
speed is a major contributory factor in around one third of all road traffic accidents.
I post the site reference.
http://www.publications.parliament.u.../557/55702.htm It does seem to contain a number of conflicting statements, particularly the section entitled "the Relationship Between Speed and Casualties", sub-section 14, has left me totally
!