Any application that uses a pressure switch can use an insulated track section and relay instead. That way, there is no weight adjustments to be made, with the attendant mental stress, and the operation will be more reliable and exact.
Simply, you can wire the track section and relay to operate when there is a train car present. More sophisticated schemes will allow a locked-in relay, and a release relay. This type of scheme, and similar ones, will allow realistic operation regardless of train length.