The VTI’s Circular Road Simulator
The Swedish National Road and Transport Research Institute has a unique circular road simulator (CRS). Under controlled conditions, the CRS implements accelerated tests that simulate the effect of traffic on roads materials (specially asphalt coatings). The history of The VTI's circular road simulator goes back to the 1940s when the construction of the VTI's circular road simulator was started on the 10th of October 1941 and finished on the 1st of June 1943, with the first actual testing started in September 1943.
The CRS has been used for different kinds of testing. The CRS and the testing methods have been developed throughout the years and currently the research focuses on testing the influence of pavement properties on particulate matter (PM) generation, generation and properties of tire wear particles, the effect of dust binding agent doses and air humidity on PM generation and the effect of traffic on the wear, deformations and texture characteristics of different types of asphalt mixes.
The VTI's CRS has six axles (of which four wheels are in operation) running on a circular test track. A separate DC motor is driving each wheel and the speed can reach up to 70 km h-1.
The diameter of the track is 5.25 m, giving an average track length of about sixteen meters. The maximum width of the track is about 0.85 m.
The track consists of twenty-eight test slabs that can be manufactured in the Lab. This means that fourteen different types of roads materials can be tested simultaneously using the VTI's CRS. The machine's central axis is fitted with an eccentric assembly and thereby all the wheels can be shifted laterally. A total of 50 mm lateral wheel wander can be achieved to distribute the wheel loads laterally. Before the test starts, the axles are lowered down and the desired axle loads are achieved. Moreover, the temperature and relative humidity in the simulator hall can be controlled via an internal air cooling system. The temperature in the hall can be varied from -5 to + 40° C and during the test, the samples surfaces can be sprinkled with water.
The measurements of cross sections made with a laser profile measurement beam that can provide more than 400 data points per slab with 0.01 mm accuracy. For each tested slab, three cross sectional profiles are usually measured. In addition, one of the wheels is provided with texture development measurement indicators to measure the mean profile depth (MPD) along the track.