A garbage collector that operates in accordance with the train algorithm designates some cars as "special" cars into each of which at most a single object is allowed. When an object in a car being collected is referred to by a reference located in such a special car, the collector may depart from the conventional evacuation approach of placing the evacuated object into the train containing the reference referring to it. If the reference is located in an object referred to from a train younger than the train in which the reference is located, the referred-to object in the car being collected is not evacuated to the train that contains the reference to it. Instead, it is evacuated to the train from which the object containing that reference is referred to.