A single-carriage reversing train positioning system which includes an extending spike-type car engaging member for engaging and moving one or more railcars. An extending chuck assembly may be provided with the ability to operate gates in bottom-discharging railcars. The system uses a single self-propelled carriage with an on-board carriage drive system that includes a drive motor which operates the car along a fixed chain situated along a guideway. A generally horizontally disposed, laterally extendable pin car-engaging assembly is mounted on the car-moving carriage for aligning with and engaging a hook loop on a railcar for moving the car. A gate-operating assembly which includes a laterally extendable chuck system which aligns with, engages and rotates gate-operating capstans on bottom discharging railcars may also be provided.