Update 12:20 p.m. Metro crews have made a preliminary fix to the cracked rail
 on the Orange and Blue lines, allowing trains to resume running on
 both tracks. 
But the agency said residual delays could continue until about 1 p.m.
 Crews plan to return overnight when the system is closed
 to make a more permanent fix, according to Metro.

Original post: Metro riders are facing another round of delays due to a cracked rail on the Blue and Orange lines, the fourth crack in the past month.