Unlike rail vehicles (where side tracks are not available), an out-of-service vehicle can be removed to the side of the road and its trolleys disconnected, allowing vehicles to pass
http://en.wikipedia.org/wiki/Trolley_bus

Unlike rail vehicles (where side tracks are not available), an out of service vehicle can be removed to the side of the roadway and its trolleys disconnected, allowing operational ...
http://www.answers.com/topic/trolleybus

The trolley or trolleys may then be disconnected from the retrieval line and secured for future use. As stated hereinabove, in selected embodiments, a processor may be programmed to ...
http://www.freepatentsonline.com/7404360.html

The following trolleys run into the waiting trolleys and are disconnected from the chain. The trolleys are accumulated in a buffer zone.
http://www.conveyor-teknik.dk/engelsk/products/type_PF80.htm ...

Over Head Monorail Trolley. General Description of Drive and Idler trolleys ... A clutch is provided to enable the drive wheel to be disconnected from the geared motor unit ...
http://www.land-rover-maintenance.fsbusiness.co.uk/Monorail% ...