Here is a list of gifs showing the expansion in various cities.
Shanghai (http://www.thatsmags.com/uploads/galleries/images/shanghai-m...)
Toronto (http://www.thatsmags.com/uploads/galleries/images/toronto-me...)
Beijing (http://big.assets.huffingtonpost.com/subwaygif2-01.gif)
Moscow (https://upload.wikimedia.org/wikipedia/commons/c/c0/%D0%9C%D...)
New York (https://secondavesagas.files.wordpress.com/2007/09/subwayhis...)