You should never remove the radiator cap on a pressurized system until the system has cooled.
Never remove the radiator cap if the engine is overheated. Steam and boiling water could shoot out under high pressure and injure you. Wait until you can touch the radiator cap with your bare hand without it feeling excessively hot. Some vehicles have coolant overflow tanks or sight glasses that let you check the coolant level without removing the radiator cap.
B If your engine overheats within 20 miles of the end of your trip, you should complete the trip and then check the problem.
C You should never shut off an overheated engine until it cools.