On 2nd February 2015, a landslide occurred adjacent to two parallel bridges on the E18 motorway: the Mofjellbekken bridges (also called Skjeggestad bridges). The landslide damaged the bridge foundations and caused the partial collapse of one bridge. Whilst no one was injured due to the sliding event, the damaged bridge was assessed as unsafe and later demolished. This paper gives an overview of the ground conditions in the area around the bridges, and presents back calculations to assess what could have triggered the slide. The back calculation indicates that a fill material placed at the top of the plateau reduced the factor of safety by 15%, which has most probably triggered the slide. The slide was restricted by the limited presence of quick/sensitive clay in the lower part of the valley and the shallow depth to bedrock near the bridge.