A clear zone is an area beginning from the edge of the travelled lane for which an errant vehicle may travel without striking any hazards. This includes adjoining and auxiliary lanes, road shoulder, verges and batters. The clear zone is determined based on a compromise between the recovery area needed for an errant vehicle, the costs involved in providing this area, and the risk of an errant vehicle in the area. Whilst a clear zone may involve frangible roadside objects, it should be kept free of any non-frangible hazards, or these hazards should be shielded by a barrier (RTA 2009).