the report describes an experiment in which geogrids were used to strengthen an existing road. the experiment was carried out during summer 1990 on road 331 at backe in the county of jamtland, northern sweden. the aim of the experiment was to determine whether reinforcement of a road pavement can reduce the amount of pavement material required and thereby help to reduce the exploitation of natural resources in the form of gravel and rock when strengthening roads with poor bearing capacity. on the test sections, the added thickness of the pavement to be strengthened was reduced from 550 mm to about 250 mm, or by about 50. the reinforcement was laid on the existing road surface, but with a thin layer (about 30 mm) of sand beneath the grid for most of the distance along the road. this was done to facilitate penetration (kaying) of the gravel from the roadbase, which here consists of crushed rock, 0-35 mm. the surface of the roadbase was levelled with a thin (about 20 mm) layer of crushed rock 0-18 mm. a wearing course of y1g (single surface treatment) was applied