This is the throttle and reversing mechanism.  The lever on the left controls the direction of the train.  The four position lever on the right controls the throttle and speed of the train. 

There are control cabs on either end of the train and the engineer operates the RDC from the forward facing control cab.  As passengers have access to the vacant cab, the levers are removed from the empty cab by the engineer. 
 
See also: Controls in a BC Rail RDC