Gunpowder, paper, printing, and the compass are sometimes called the Four Great Inventions of Ancient China. Kites were first used as a way for the army to signal warnings. Umbrellas were invented for protection from the sun as well as the rain. Chinese doctors knew about certain herbs to help sick people.
It was a huge success with 38,000 passengers on opening day. Because there were no ventilation shafts, the smoke would accumulate, and the drivers would be coughing all the time. The use of steam trains underground led to some health complaints, but when electric vehicles, such as trams were built in the early 1900s, the underground was modernized.