The Austrian guideline regulating pavement design is currently being revised in the light of increasing heavy vehicle traffic and changes in the technical equipment of heavy freight vehicles. To calculate the expected traffic load for the design period the modification will not longer employ the well-known Fourth Power Law. Instead the damaging impact on the pavement structure (with fatigue as the criterion) is determined in a direct approach from the fatigue effects due to the passage of different axle loads and axle configurations.

A comprehensive sensitive analysis examines the key components of fatigue caused by single and twin tyres and different axle configurations on asphalt pavements by taking into account their lateral distribution in the cross section of a road lane. Detailed data for lateral distributions of loads evaluated due to field measurements and comprehensive information on the distribution of axle loads and heavy vehicle types found in Austria's federal road network provide the basis for computation of mean equivalency factors for different vehicle types and characteristic collectives of heavy freight vehicles. These are used to determine the relevant design load for routine design purposes and will be incorporated in the modified Austrian design guideline for asphalt pavements.