>>6364849 pb

Could be many factors... Trying to slow down by weaving vs. straight ahead or looking for something in dash area to help - distracted.

Wrong gear going down grade? If manual trans., going too fast to get in a lower gear.

If he hauling lumber, it's a heavy load, close to 80,000lb GVW. Would like to see a wt. ticket on that load, if lumber - They used to like to overload that freight.

No Jake Brake?

With air brakes going downhill, don't take foot on and off hot brakes - Will let oxygen in and catch on fire.

Should have taken truck runaway. English prolem?

Brakes could have been out of adjustment prior to. Must be certified to adjust own air brakes - take class - not hard.

Older trucks used to be equipped with trolly brakes (lever for the trailer brakes only), which could help aid in holding the whole rig back. Guessing this truck didn't have one and wouldn't have helped if already going too fast.

All of these issues are driver error. Unless of course, it's a newer truck that can be taken over by remote control.