New York City's F and M subway lines are permanently switching routes starting Monday. Riders in Manhattan and Queens have been preparing for the change, which the MTA hopes will reduce train congestion. The swap officially took effect at 6 a.m. Monday and runs on weekdays through 9:30 p.m., with no change to late-night service on either line. Officials say the swap reduces the number of trains that have to merge or cross, especially at bottlenecks at Queens Plaza. | CBS New York