When operating a heavy passenger coach down long, steep mountain descents, why is continuous friction braking dangerous, and what is the correct operational method?

1. Continuous friction braking causes severe brake fade (热衰退) and total brake failure; drivers must pre-select a low gear to utilize engine compression braking and auxiliary retarders (缓速器), strictly prohibiting neutral coasting
2. Continuous braking overheats the air conditioning compressor; drivers must coast in neutral (空挡滑行) and use the handbrake
3. Friction braking causes the steering wheel to reverse its turning direction; drivers must turn off the engine ignition while descending
4. Continuous braking charges the battery excessively; drivers must accelerate intermittently to discharge the alternator