Sub-contract tipper articulated wagon rollover on site whilst delivering aggregates.  Five previous articluated loads had been tipped that day. Previously soft ground in the tipping area had become rutted and then frozen, which created a crossfall which had not been identified by site staff.   Driver remained in cab and crossfall not present at that end of the wagon.  Wagon body rolled over and cab stayed upright.  No injuries or additional damage caused other than to wagon body.  Wagon recovered safely.  The investigation found that the cross gradient of the access road at the rear of the chassis was, on average 1:13 (7.7%) and this is likely to have been a significant contributory factor in destabilising the articulated load in addition to the frozen ground conditions.   Artic tipper wagons banned from site. Safety alert issued to all sub-contract hauliers and by main contractor to their staff.Sub-contract tipper articulated wagon rollover on site whilst delivering aggregates.  Five previous articluated loads had been tipped that day. Previously soft ground in the tipping area had become rutted and then frozen, which created a crossfall which had not been identified by site staff.   Driver remained in cab and crossfall not present at that end of the wagon.  Wagon body rolled over and cab stayed upright.  No injuries or additional damage caused other than to wagon body.  Wagon recovered safely.  The investigation found that the cross gradient of the access road at the rear of the chassis was, on average 1:13 (7.7%) and this is likely to have been a significant contributory factor in destabilising the articulated load in addition to the frozen ground conditions.   Artic tipper wagons banned from site. Safety alert issued to all sub-contract hauliers and by main contractor to their staff.