Being a Sunset Route guy, I've been fortunate in not having to operate on icy rails, but I've heard plenty from of those that have had that experience, first hand.

I have had the similar experience ("experiment") with the laws of physics, a choo-choo, and Wesson Oil. Ice is, in some ways better, because once it melts and evaporates from truck and brake friction, it isn't as much of a problem. Where as, every time you pull a cut of leaky/spill vegie oil, you re-lubricate the rails your running over. So I used....sand....lots and lots of sand, and power on the jam to keep the brakes "hot", complete with the aroma of burning vegie oil, but without the French fry's....

If this was possibly weather related, then one really shouldn't have been running at a speed where weather conditions such as possible icing could impede control, and that is a matter of good procedures, training, and experience, by both operators, and operations managers.

But, it's the same reason the CHP tells you to slow down to a "safe" speed in ice and snow.....