I recall a news photo of one of the monster N&W coal trains in
a contemporaneous issue of Trains magazine. I think N&W was just
trying to push the edge of the envelope... Obviously it didn't
work out that well, but BNSF and UP today regularly run 20,000 ton
trains safely, for very long distances.

Makes me wonder how fast diesels would have taken over if work
rules simply specified a 12 hour day without any mileage limit.
Clearly with a mileage limit there was a powerful incentive to
run trains more slowly and with heavier tonnage. Still true today.

Tim