An automatic coupler allows two vehicles to be attached to each other merely by pushing the two vehicles together. There are various types and systems in use, which range from a simple automatic mechanical coupler (like the 'buckeye coupler' of US origin) to one which is remotely controlled and can connect and secure air and electrical connections in one operation. I cannot recommend automatic couplers because they can cause a lot of technical trouble. Careful specification and attention to design detail is required to ensure reliability. One is mindful of problems suffered by MUNI in San Francisco on their Boeing LRVs and by Eurotunnel and London Underground, all of whom use complex automatic couplers. Good advice is not to use them. Automatic couplers are expensive to repair after even minor collisions or 'rough shunts' as they are often called to reduce the operating manager's anger.