Transports for excavators

Add a trailer that a truck or a special vehicle can connect to (small for small trucks and excavators and so on) that will be stored in a special building (something like a parking it could be also used for other machines) when not in use and when an excavator needs to move a distance longer then x a truck gets the trailer moves the excavator to the destination and returns the trailer to storage. You can also add an option the change the minimal move distance or turn it of completely.