How often must a driver inspect a placarded hazmat vehicle's tires?

Federal rules require placarded hazmat drivers to examine tires at the start of each trip and each time the vehicle is parked. A leaking, flat, or overheated tire on a hazmat vehicle is a fire risk that can ignite the cargo or release the contents. If a tire is found to be defective, it must be replaced before the trip continues. Use of the spare tire as a temporary fix is allowed within reason, but a damaged tire on a hazmat load cannot be ignored. The rule applies even on short stops and even at fuel stops. The walk-around and tire check that takes two minutes can prevent a roadside fire that ends careers and lives.