DP going up and down mountains

Go down the hill at a speed your engine or exhaust brake will maintain a constant speed-not speeding up or slow in down.. If you have an engine or jake brake you can slow down faster than you can with an exhaust brake. It is best to start down at that speed rather than start down too fast and have to use the service brakes to slow down to that speed. Saw one coach that burned to the ground because the brakes got hot burned and then burned the coach down. Experience is about the only thing that will tell you what that speed is. Until you get the experience go slower rather than faster. The reason for slower is because the engine will upshift with no input from you to keep from over reving if it gets going too fast. Trying to slow down a runaway coach is where the damage, including ruining brakes and fire comes in.