"Do Not Hump" oversize/high/wide railcars ... ;p llbbbbt !
I have 2 working hump yards which have a short segment of track, a slight 2% upwards gradient, just before the hump ... and a gentle 0.01% gradient downhill, after the hump.
I place a RR worker, (as a marker) where the pin puller would be, at the apex of the hump, and I "AI" "Autodrive" the to-be humped consist at 4 mph, whilst I press Ctrl+D (decouple) and watch the railcars unhook & roll, all the while I change the many turnouts directions, downhill.
Makeshift retarders are easily made, with several uphill opposing short segments of 1% gradient tracks, that railcars encounter while rolling downgrade into the classification bowl.
You can even place several "AI Brake" units (which an invisible locomotive) at the exit of the yard to stop run-through runaway railcars.
I even have experimented with many "AI Brake" units all throughout the conist (which essentually makes a fake, drivable draft of railcars), that I can apply braking to.
There might be some sort of other assets that can be placed at the classification yard exit, that could also slow, or stop, runaways, but I haven't experimented with these devices yet.
