When descending a long, steep grade, a driver should brake until the vehicle's speed is about 5 mph below the 'safe speed' and then release the brakes. Why is this 'snub braking' technique recommended?

1. To allow the brake drums to cool and prevent brake fade
2. To keep the air pressure from dropping too quickly
3. To ensure the trailer brakes are working harder than the tractor brakes
4. To dry out wet brake linings