I've killed lots of trains and one truck convoy on-line, but when I go off line, the roads don't seem to be there. The trains are fairly easy to spot from long distance, as they have a nice smudge of black smoke that follows them. The truck convoys are very hard to spot. The only way I found that one was to find a road and follow it at low level for many miles. I haven't quite figured out which facilities trains spawn from, but they are fun to kill.
I would like to see it be a little harder to kill them then they are. The engine should be easy to halt, but destroying boxcars should be a little harder. I'd also like to see a new facility type added, the railroad marshalling yard. Hitting it should increase the interval between train spawning. I'd also like to see rail and road brides that can be taken out to halt traffic to a particular base/facility. They should be fairly hard to damage, requiring a direct hit from a 2K bomb to significantly damage.