The union agreed to cutting down train crew size and getting rid of an extra front cab crewmember, the fireman, some time ago. It also agreed to eliminating a crew member position in the rear of the train by eliminating the caboose and replacing it with a tail light.
Positive Train Control, the system receiving so much attention in the news since this crash, is capable of operating the train with no on-board human operator. It is currently used on a number of light-rail systems.