One of the frustrations returning to Saigon from Shanghai, China, was having to get used to a city with no subway. I just wish that Vietnam could develop their subway system as fast as the subway system in China.
See the chart below, it is amazingly how fast the subway system spread across the country. Someday a person will be able to enter a subway system in Shanghai and travel to, say, Xian without ever having to leave the rail system. That is amazing.