On a long downgrade with a doubles or triples combination, what braking approach keeps the vehicle under control?

Long downgrades are managed primarily with the proper low gear selected before the descent, letting engine braking help control speed, combined with a controlled braking technique that keeps the brakes from overheating. Continuously riding the brakes causes them to overheat and fade, which is extremely dangerous with a heavy, long combination. Coasting in neutral is illegal and unsafe. The driver chooses a safe speed for the grade, uses the gearing to hold it, and applies the brakes firmly enough to control speed without keeping constant light pressure that builds heat. With multiple trailers, a runaway on a downgrade would be nearly impossible to recover, so preparation before the hill is critical.