One example of the most demanding infrastructure in terms of maintenance are the airports. Airport authorities have the imperative task to keep the airport opened at any weather condition, also in winter where the presence of snow might create delays, which are found unacceptable for the community. Therefore the airport maintenance personnel have to perform maintenance operations to keep runways opened. One of the established ways for checking if the airport maintenance operations are efficiently performed is to measure friction over the maintained surface. If the pavement surface is efficiently maintained it provides enough grip for the plane to perform its maneuvers (while departing and landing), which in turn means that friction measurements have to be accurate, reliable and repeatable.
Developed by ViaTech AS in collaboration with the Norwegian Public Road Administration, the ViaFriction is used as a reference for measuring continuously the longitudinal friction on roads and airports since 2006 according to standards (ASTM E1551-08, ASTM F408-99, CEN TS 15901-2, CEN TS 15901-14). This system is also used for approval of newly built roads and also for accident reconstruction. Based on the seasonal period, there are two ViaFriction systems which can be used: the summer and winter system.
The ViaFriction summer unit consists of a trailer with a water tank of 1000l which sprays an adjustable amount of water ranged between 0.5-1 mm in front of the measurement standardised wheel, while the ViaFriction winter unit is a light portable unit easily attachable to the rear part of a normal passenger car. The measuring system in both the units follows the same principle and has the same components where an 8in wheel is forced to rotate at a lower speed compared to the vehicle speed and in longitudinal direction. The difference in speed between the vehicle and the testing tyre enhance rotational slip and the corresponding friction is detected.
The accuracy of the ViaFriction measurement unit relies on the components of its system such as advanced trasductors and last generation system controllers. While trasductors provide accurate measurements as for the rotating speed and slip of the standardised measuring wheel, the advanced system controllers enhance the adjustments in real time of differentials. The real time adjustments avoid any possible delay in the measurement, guaranteeing the correct measurements in real time and subsequently at the interested set levels. Direct consequence of the described system is a fast and accurate system response.
The above figure shows the seven friction measurements of a same friction unit after a harmonisation process. Over a testing road surface of 1,000 meters and for all the seven measurements the friction average result has a maximum difference of 0,02.
