The article mentions the MTA has a constraint of never shutting down a line, but this conveniently ignores the fact that the B line was split into two pieces for ~ 18 years (1986-2004) while the track on the Manhattan Bridge was being reworked.  The fact that it took 18 years to rework this 1 mile length of track points to the real issue, not the fact that NYC cannot accept &quot;downtime&quot;.