When designing roads it’s important to know what loads will be driven on it. The axles on heavy vehicles can either have super single tires or dual tires which, according to studies, damage the roads differently. The Swedish Transport Administration is developing an understanding for the character of these different kinds of axle and tire types on the loads induced on Swedish roads. In this thesis a field study was conducted to determine the distribution between axles with super single tires and axles with dual tires on heavy vehicles. A highway, a country road and a national road were investigated during the study. The result showed that the number of trucks with single tire axles, i.e. those with super single tires, varies between 39 and 48 percent on the different types of road. That the truck has a single tire axle means that the truck has at least one axle with single tires in addition to the steering axle. A small study was conducted to determine the width of tires on heavy vehicles. A comparison of trucks with single- and dual tire axles was carried out in terms of degradation of the roads. Permanent deformation of unbound layers and fatigue cracking were investigated since these degradation mechanisms are currently used as design parameters in the design of roads. Load values from Bridge Weight In Motion (BWIM) data were used in the calculations and vehicle type 113, 123 and 12211 were investigated. Permanent deformation and fatigue cracking were calculated according to the criteria given in ATB VÄG 2005. Dissipated Creep Strain Energy (DCSE) has been calculated for the selected truck types. The study showed that trucks with axles with single tires accelerate the degradation of the roads. The permanent deformation was almost the same for the two different kinds of axle types.