 These would result in a 'loose-coupled train' in which the buffers of adjacent vehicles would only touch when the coupling chain was fully slack, such as when being pushed or going down hill.Although the buffers in the very earliest days of railways were rigid ("dumb buffers"), they soon came to be spring-loaded, while those fitted to modern locomotives and rolling stock incorporate oleo-pneumatic shock absorbers.The original English buffers were the same on each side, so that there was a small tendency for buffers to slide off each other.