Few things are more frustrating in TransCAD than editing Transit Route System (.rts) files. Here's a great error from a TransCAD log file:
“Route ID (369) not greater than previous (376)”
Thanks Captain Obvious!
If you ever run into an issue like this, simply edit the Transit route with the lowed ID number so that it will repopulate with an ID "greater than previous".
Next, delete the change and you should be good to go.