Mr. Daly ellTo ask the Secretary of State for Transport what research his Department has done on the relative safety and accident incidence of tyre tread depth of(a) 1 mm across the whole width of the tyre, (b) 1 mm across 75 per cent, of the tyre, (c) 1.6 mm across the whole width of the tyre and (d) 2 mm; and if he will make a statement.
§ Mr. Peter Bottomley[holding answer 27 November 1987]: The Transport and Road Research Laboratory has done research in this area for many years. TRRL Supplementary Report 672, published in 1981, describes work on braking force coefficients of worn tyres.
The results of work in 1985 on the effect of tread depth on wet cornering force coefficients of car tyres, was circulated to all organisations consulted as part of the review of the tyre tread depth regulations in 1986.
A copy of the working paper is being placed in the Library.