"When they finish the Second Avenue Subway, this apartment will quadruple in value." [0] Mad Men had real estate agents promising the subway in 1965. Of course, the US$28k apartment in question is now worth about US$1MM, so it's true that the value will quadruple -- times at least ten.
It's also likely easier to move faster when the public is more forgiving of worker deaths. No idea on cumulative statistics, but the following headlines are illustrative:
SHANGHAI: Two men were killed and six others were injured here yesterday in two separate incidents at subway construction sites. [1]
5 dead and 18 injured in Shanghai Metro Line 12 construction site accident [2]
Not Shanghai, but...
On Nov 15, a subway tunnel under construction collapsed in Hangzhou, Zhejiang province, killing 17 people. [1]
New subway lines have to connect into existing running subway lines. Digging the tunnels is usually the easy part, it's the points where they connect to things that is hard.