Employee was operating a haul truck down a haulage ramp with another truck ahead of EE. As EE neared chutes EE was pulling from, EE saw other truck backing into the chutes so EE shut off the drive lights & went to brake but missed & bumped the throttle causing EE's truck to contact the bed of the other truck & then the rib. Doctor restricted EE for 1 shift for wrist sprain.