YOU WANT TO BUILD A WHAT? Suppose you get the idea that a steam-powered stationary pumping engine might be put on wheels and used in lieu of mules or oxen to pull mine carts. (This idea was first tested 200 years ago. Expect additional commemorative posts as the school term winds down and the summer break begins.) Once the concept has been demonstrated with mineral loads, somebody has the idea of using the same technology, albeit with different kinds of carts, to transport people. People are live loads, capable of self-loading. What does a facility for such loading look like? The first one survives in Manchester, England (the one at the Liverpool end has been extensively reworked) and the Transport Blog writers (taking advantage of a meeting with the Live from the Third Rail writers, offer a guided tour.
There is a great deal more habit persistence in British railroad technology than there is in the United States. Floor-height platforms? We built step boxes. Passenger cars based on stagecoach technology? We lacked the patience to hang all those side doors. Across the pond, the window arrangement of the British Railways' Mark I coaches is a clear descendant of the old stagecoach design; an exhibit at the National Railway Museum in York illustrates this.