"Lost his airbrakes" makes no sense at all. A train's brakes are "deadman brakes"--that is, if you lose the air, the brakes come on; they are held off from application by the air. So unless you think that the application of brakes caused the accident, it wouldn't be "lost his airbrakes".
Uncle DaveO, highway truck brakes are true deadman brakes - mechanically applied by a spring, released by air. Train brakes aren't.
The brakes on a train (improved since the 1903 wreck of the '97 but still work about the same way) use air to apply the brakes and to release. There's an emergency reservoir that holds the air needed to apply the brake if the valve detects that the air pipe has broken. But if the engineer has overused the brakes, consuming more air than the compressor in the locomotive can replace, the whole system bleeds down and - for a while, until the system recovers - you don't get adequate braking force. No big deal unless you happen to be coming up too fast on a sharp curve...
Another thing -- I had long wondered why on earth did he have his "hand on the throttle" if he was trying to slow down? It turns out that railroad people investigating the wreckage found that he had thrown the loco into full reverse, a desperation move that didn't work.
"Lost his averages?" Man, that's really stretching the limits of the language. Someone's poetic license ought to have been revoked for that.
Cheers
-HM