4.4. Friction
In order to assess whether any changes in skid resistance
measured on the BOF sections were related to variation that would
have occurred on the test road, the three test sections were periodically
surveyed for friction. Pavement skid resistance was measured
by the British Pendulum Tester according to ASTM E303
and expressed by a British Pendulum number (BPN). This test measures
frictional properties by determining the loss in kinetic energy
of a sliding rubber shoe when it is in contact with the pavement
surface. All the measurements were taken when the air temperature
reached about 25 C. Changes in BPN values over time are
shown in Fig. 7. Test data were averaged for each section and for
a longitudinal position (left and right wheelpaths) for the British
pendulum test device.