Reducing the Rut Depth of a Thin-paved Road by Controlling the Driving Lines of Heavy Trucks

Deepening of ruts due to heavy trucks driving constantly the same driving line on thin-paved roads is a significant problem to road maintenance. The problem is worsening as truck weights and truck traffic volumes are increasing. Especially rapidly ruts can develop during the thawing period of seasonal frost. As rut depth increases, longitudinal cracks may develop and the bearing capacity of road deteriorate also outside of the thawing period, since ruts are gathering rainwater and cracks allow it infiltrate into the road structure. There are plenty of this kind of thin-paved low-volume roads, which may be occasionally exposed to intensive heavy truck loading, when for instance timber is harvested on the region.
In an earlier study funded by the Finnish Transport Infrastructure Agency it was noticed that a heavy truck can uplift road surface even at distance of 1.5 to 2.0 m from the driving line. Therefore, it was decided to test if it is possible to reduce rut depth by controlling the driving lines of heavy trucks. Loading tests were carried out using seven-axle log trucks weighing 64 tons instantly after the frost thawing. The vertical movements of road surface were measured using two displacement transducers, one located at the wheel path and the other one 0.5 m apart from it, while the development of rut depths on a longer road section was monitored using a laser scanner.
The results clearly indicated that by controlled variation of driving lines it was possible to restore a major part of rutting developed by the preceding heavy truck overruns. This observation has great practical significance regarding autonomous traffic when in the worst scenario all heavy vehicles are guided to the same driving line.