To study texture of pavement surfaces and its effect on pavement friction, this article features a field experiment conducted on in-service pavements to characterize surface texture by spectral analysis to substantiate links to friction values. Pavement friction was measured using a Mu-meter and British pendulum tester whereas texture data was collected using a stationary laser profilometer. Texture spectra were analyzed and expressed in third octave bands. The correlation between texture spectral levels and friction values at different speeds are discussed in the paper. Results show that the texture level, including spectral band levels, can well represent texture characteristics, as texture spectral levels have a good correlation with friction coefficient, especially the texture level of texture wavelengths at 1.25–12.5 mm versus SFC_sl (representing the slope of the side force coefficient (SFC) versus speed), i.e., the slope of friction versus speed. This friction parameter gives better correlations with texture parameters than friction values at different speeds, which is believed to be an effect of the drainage caused by texture in that wavelength range.

The depth to which the pavement texture is enveloped by the tire tread rubber (d) is an important parameter related to contact performance. This study presents a new method (S-BAC), which relies on the ratio between the real contact area and the nominal tire-pavement contact area (S) and the bearing area curve (BAC), to measure the depth on pavements. The tire-pavement contact was simulated by contact between a non-patterned rubber block and pavement specimens. After analyzing the affecting factors, the new method was compared with previous methods by the d values and the application on the relationship between pavement texture parameters and friction. The results reveal that though there is a linear regression between the d obtained with the S-BAC and previous methods, the d values obtained with different methods differ. Applying the S-BAC method can strengthen the relationship between texture parameters and friction more than other methods.

The EU requires vehicle tires to be tested for noise emission and labelled. Some other countries also have similar procedures. Preparations for labelling of acoustical properties of road pavements is also ongoing in EU. Road vehicles and their tires must be tested and meet noise limits worldwide. However, all cases involve problems with measurement methods and conditions, which create uncertainties higher than desirable to make fair decisions on which product to select. For tires and road vehicles the major obstacle is the test track surface, which cannot be sufficiently well defined and reproducible. Also, far from all products (tires) are measured, so commonly only the noisiest products are correctly labelled. Although attempts are made to go indoors to do the measurements, they are still for the foreseeable future going to be made outdoors, with all the influence of weather and seasons that this causes. The author has worked most of his long career with such issues and in this paper, the author outlines his vision of how most of the problems (uncertainties) can be reduced to acceptable levels, mainly by making measurements indoors, with reproducible and representative conditions for both the labelling and the actual noise emission in traffic.