Oh no, I seem to have had mods enabled (K2) that changed the results a bit. I apologize, that is my mistake for being inattentive. I have removed the misleading data from my post above. Here are some more accurate results for the humble roundabout:

1-1 score: 58.76 (90-min test)
1-1-1 score: 38.55 ...

It's obviously bad for longer trains, which this thread is clearly focused on, but I would like to at least document the humble roundabout. It's not megabase worthy, but I like to do smaller-scale grid-based stuff for easy supply chain management with 1-1 trains, so it's very useful to know about ...