Apologies, I haven't been through Colorado in years, but it makes sense for trucks to stay in low gear in those situations, while engine braking for a regular car in a dangerous area is just that, dangerous. Cars around you won't see a brake light and won't know that you're "braking". I've seen on some cars these days that while they engine brake the brake lights go on, which I think makes sense.Dont believe thats correct. At least in Colorado. They have signs everywhere telling trucks to stay in a low gear. However they do have signs that say "engine brake mufflers required".