Division 5.2.2
United Kingdom
The adhesion utilisation (ε) shall be measured on road surfaces with a coefficient of adhesion of 0,3 or less, and of about 0,8 (dry road), with an initial speed of 50 km/h or vmax, whichever is the lower. To eliminate the effects of differential brake temperatures it is recommended that zAL (see Appendix 1) be determined prior to the determination of k.
Until such test surfaces become generally available, tyres at the limit of wear, and higher values up to 0,4 may be used at the discretion of the technical service. The actual value obtained and the type of tyres and surface shall be recorded.