The general usage of the phrase electric train, is referred to a whole unit consisting of large number of coupled carriages (passenger or freight) hauled by an electric locomotive instead of the earlier steam locomotive, or a unit with smaller number of coupled carriages which have independent electric drive motors underneath the chassis (undercarriage), controlled by the driver at one end of the train, from a small cabin. The difference is only in the type of hauling or drive mechanism used. The latter form is common in public transport, where a drive car can be coupled with one or two other cars to form a group that can be easily joined to another group at peak travel times.