A method (300) of controlling an internal combustion engine (3) of a vehicle (1), comprising: receiving at least one input (301) indicative of a current external environment proximal to the vehicle (1); determining (305) in dependence on the at least one input (301) whether a hazard is present; determining a current propulsion demand (303) of the vehicle (1); if it is determined that the current propulsion demand (303) is low, either commanding switching of the internal combustion engine (3) to an off state (307) if it is determined that a hazard is not present, or not commanding switching of the internal combustion engine (3) to the off state if it is determined that a hazard is present; and if it is determined that the current propulsion demand (303) is high, commanding switching of the internal combustion engine (3) to an on state if the internal combustion engine (3) is in the off state.