8. Procedure
8.1 Bring the apparatus to the desired speed and deliver water to the pavement ahead of the test tire. Approximately 0.5 s after beginning of the water delivery, apply the test wheel brake so as to lock the wheel completely. The wheel shall remain locked for the duration of the data averaging interval (8.4.1).
8.2 Water delivery may be terminated as soon as the brake is released.
8.3 Record electrical calibration signals prior to and after testing each section, or as needed to ensure valid data.
8.4 Data Evaluation—-Evaluate the resulting skid-resistance records as follows:
8.4.1 Mark the point of wheel lock-up and measure the data from a point not less than 0.2 s after this mark for an interval not less than 1.0 s nor more than 3.0 s. Average the data between these points and use the mean value to read or to calculate the skid number.