That's correct. I mentioned that I use the disable method to remove objects and it works with splines which can't be deleted enmasse from a route. By disabling the asset, it will be considered a missing asset according to the route. By running delete missing assets, this will remove the reference to this object within the route and not remove the asset from the Trainz content. After the asset is removed from the route, and the route is saved, exit from Trainz and enable the asset again in Content Manager.