So here they are, maybe others have ideas also.
Landslide - some mountain falls down, and buries your rail line, you have to figure out a new way through it. Particularly bad if it's a heavy multi-track route.
Chemical accident / terrorists - half a city goes away, affecting its supply and demand
Environmentalists protest at oil refinery - it can't accept oil for a while
Train robbery - of passenger or goods trains
Coupler malfunction - the last few cars of the train fall off and stay there, or roll downhill, until you send the train back to retrieve them. Could be very awkward
Hurricane - blows a train or truck off a bridge it's crossing. Even better if it blows down all the trees also, and some buildings
Tornado - well, we can all imagine that one.
Yes, the subs torpedoing ships would be great. Particularly bad if it's a passenger ship. If it's an oil tanker, there can be an oil slick
![Twisted Evil :twisted:](./images/smilies/icon_twisted.gif)
Random bridge collapses, or tunnels, maybe catching a vehicle