The Swedish road administration requested that an independent entity facilitate friction tests with several types of friction measuring devices on three types of prepared ice surfaces. The objective was to evaluate lateral low slip measuring devices against longitudinal high slip devices, and evaluate how they measure road grip, i.e. friction differences between surfaces. The first surface was macro rough and micro smooth, the second was macro- and micro smooth and the third was macro- and micro rough. These tests were performed on Lake Kakel near Arjeplog, northern Sweden on March 18th, 2008. Weather conditions were stable with ice temperatures between -4°C (24.8°F) and -3°C (26.6°F). Tests showed that changes on the ice surfaces were readily detected with all four of the lateral low slip friction measurement devices and the two longitudinal high slip devices. Friction resolutions were higher with low lateral slip devices compared to high longitudinal slip devices. The tires on the devices were of different type and are the main reason for the difference in friction resolution. One major difference was detected; the lateral low slip method measured the friction between its regular winter tire and the macro rough, micro smooth surface tobe higher, compared to the friction on the macro- and micro rough ice surface where the longitudinal high slip devices measured the friction between its industrial friction tire to be higher on the macro- and micro rough ice surface.
Abstract