Emp #1 was operating a ramcar & was parked behind a miner. Ramcar lights were off while ore was being loaded. Emp. #2 was driving another ramcar in reverse, approaching the miner with trailer lights off. Emp #2 didn't see Emp #1 being loaded behind the miner & bumped Emp #1 ramcar. Emp taken to Er per request. Prescription given for pain. Emp. back to work with no restrictions.