Amsterdam : 1m
Antwerp : 0.6m
Brussels : 1.2m
Barcelona : 1.7m
Copenhagen : 0.7m
That said, places like the SF Bay Area and Southern California, are unlikely to get a large enough train system to be an alternative to cars anytime in the next 50-100 years. Adding 1-2 lines every 10 years is not enough. You need a extensive system. It needs fast express lines so that people making trips from one side to the other can do so in a reasonable amount of time. AFAIK the LA system they are sssslllooowwwlllyyy rebuilding, has only slow every-stop lines. It's, on average, door to door, going to be over 3hrs from the west side of LA to the east side of LA. Even if you live directly next to the station and need to go so some place next to the station on other end it will be 2hrs.Highway 401 in Ontario is the largest highway in North America, up to 18 lanes wide. It moves 500,000 cars per day; fewer than a single subway line.
The incredible cost of building and maintaining it, the cost of 500,000 cars and fuelling them, the enormous land use, the environmental cost of the concrete, the idea that you could have a pleasant place to live or work near it... but we can't have trains which move more people, less pollutingly, less dangerously, in less space, are nicer to be around, and overall costs less, because it isn't profitable? As if Highway 401 is profitable?