An experimental study of the friction coefficient is performed for a tyre tread block in rolling and sliding contact with two different asphalt substrates, a smooth aluminium and an anti-slip tape substrate. The sliding friction coefficient is for all substrates seen to increase as the sliding velocity is increasing. However, the slope for the increasing friction as a function of sliding velocity differs significantly between the substrates, presumably due to differences in the respective contribution from adhesive and hysteresis friction mechanisms. Parametric studies of the rolling friction show that the choice of substrate as well as the rolling velocity and the slip ratio has significant influence on the resulting friction coefficient. A linear relation is observed between the longitudinal rolling friction coefficient measured at low values of slip ratio and the sliding friction coefficient measured at low sliding velocities. For the tests of rolling friction at higher values of slip, stick\textendash slip conditions are observed for which the frequency content of the longitudinal force is seen to vary substantially between the different operating conditions and choice of substrate. The outcomes of this study can potentially be used to improve future tyre\textendash road contacts with respect to wear, traction and noise generation.