Question When refueling a vehicle transporting hazardous materials: Answers The engine should be left on. The engine should be turned off. The gas nozzle may be left unattended. Someone other than the driver should do it. Explanation Always turn the engine off before refueling a vehicle carrying hazardous materials. Someone must always be at the nozzle controlling the fuel flow. Take a FREE Practice Test Now This questions appears in the following tests: District Of Columbia HazMat , South Carolina HazMat , Tennessee HazMat ,