it's normal for a train to be made up of multiple independent units[1], which are then coupled together to make a longer service each unit has two cabs (one at

it's normal for a train to be made up of multiple independent units[1], which are then coupled together to make a longer service each unit has two cabs (one at each end) a common configuration is a 12 coach train made up of 3 x 4-long-units, which would have 6 cabs that's a lot of upgrading [1]: http://extra.southernelectric.org.uk/news/southern/img/colinduff-377609vic1556dkg-vic+377617vic1556cat-vic-form1701vic-epd-121213-450.jpg http://extra.southernelectric.org.uk/news/southern/img/colin... [2]: http://extra.southernelectric.org.uk/news/southern/img/colinduff-377604+377606clj1123vic-epd121213-450.jpg http://extra.southernelectric.org.uk/news/southern/img/colin...