Due to low structural strength, special restrictions on allowable axle load are enforced during the spring thaw period on 52% of the national roads in Akershus County. For the county roads, special axle load regulations are enforced on 50% in the summer and the autumn season, and on 90% in the spring thaw period. In order to facilitate road transoirt the Public Roads Administration wishes to apply an axle load limit of 10 tons to the public road network in general with a minimum of special regulations. In order to achieve this, however, structural strengthening of the roads is necessary. This publication presents a method and a tool for analysing the need for strengthening based on changes in the functional performance with respect to time and to the volume of the heavy traffic. The analysis is executed in two steps. The objective of the first step is to locate the roads where a need for strengthening is likely to be present. For the second step of the analysis, a model based on "the functional service life" of the pavement is developed. For the evaluation of required strengthening, a computer program named FORAN is developed.
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