An average passenger vehicle at 55 mph can stop within 300 feet. How much room can a large vehicle need at the same speed?

Why

Same speed, a hundred feet more road. The handbook puts an average passenger vehicle at 300 feet to stop from 55 mph and a large vehicle at up to 400 feet, and it adds the part drivers forget: weight and speed both stretch that distance, so a loaded truck needs more room than an empty one. That gap is the reason for the rule you should actually change your behavior for, which the handbook states as a consequence rather than advice: do not pull in front of a large vehicle and then slow abruptly or stop, because it cannot shed that speed in time and ends up in your back bumper. Five hundred feet is a real number in the handbook, but it is where you dim your high beams for an oncoming vehicle.