To expand upon the specific discussion of the OP, I feel we are witnessing a historical pattern: urban-flight -> under-valued urban real-estate -> then urban re

To expand upon the specific discussion of the OP, I feel we are witnessing a historical pattern: urban-flight -> under-valued urban real-estate -> then urban renewal and economic opportunity -> influx of homeless and criminals since high-population density is good for both -> then public criticism that the cops are too heavy handed -> cops less likely to enforce + strain on infrastructure and services (like mass transit) + urban unrest due to economic disparity -> urban-flight -> ... If the problem is that the BART is operating beyond capacity, adding capacity might not matter if the population is set to decline for the other reasons stated.