Simplified topology for trolley assist-capable electric drive truck

A trolley assist-capable electric drive truck (20) includes a DC link (40) with first, second and third contactors (41, 42, 43) that may be opened and closed in different configurations to operate the truck in different modes. In a normal propel mode, the three contactors are open and electrical power is routed from an onboard electrical power source (23) to electric propulsion motors (26). During normal retard mode, the three contactors are closed to route electrical energy generated by the electric propulsion motors (26) through a grid resistor (56) of the DC link (40). In a trolley mode, the first and second contactors (42) are closed, but the third contactor (43) is open, and electrical power is routed from the trolley lines (11, 13) to the motors for propulsion, or in a reverse direction for retarding the truck.