When there are enough passengers to justify it, single unit powered railcars can be joined in a multiple-unit form, with one driver controlling all engines, however it has previously been the practice for a railcar to tow a carriage or second railcar which does not provide any power.
There are also articulated railcars, with bogies under the point between the carriages rather than two pivoting bogies under each carriage (see Jacobs bogie).