How did the subways system develop over time?

Question

How did the subways system develop over time?

Answer 1

from horses to steam to cables to electric to humm what are those super fast ones run by

Answer 2

http://homepage.ntlworld.com/clivebillso...

http://www.british-history.ac.uk/report....

Answer 3

Subway systems were first conceived on the London Underground.  With London having such a long history, by that time the city was so dense, there was no room to build grade-level rail.  So they built below-grade, AKA a subway.  Trains were first steam locomotives, then electric in the late 19th century.  Obviously, one railway line is not enough to accommodate the whole of London, so the Underground introduced more and more lines up until today, where it is one of the world's most extensive subway systems.  This type of rapid transit didn't get introduced to North America until roughly the early 20th century, when Boston opened the Green line.  Then Asia caught on closer to mid 20th century.

Answer 4

They installed them in the busiest part of town then as the own grew they added lines.