Express vs Local

Copyright 2008 by Paul Niquette. All rights reserved.

Here you see an excerpt from the subway diagram for the borough of Manhattan.  Five lines provide both express and local service for a total of 78 stations.  Passengers at 32 stations can board either express or local trains.  Express trains necessarily bypass a total of 46 local stations.
In  fixed-guideway public transit systems, offering parallel express service is extremely costly...
  • Construction expenditures for each rail line must be doubled to cover the requisite tunnels and trackage. 
  • Capital expenditures must cover additional rolling stock. 
  • Express service increases the number of platforms at each express station, along with expanded concourses.
  • For passengers, extra street level entrances are required, along with support for circulation between concourses and platforms. 
  • Life-cycle costs for operations and maintenance are impacted for express train service, not to mention energy consumption. 
Express train service must confer enormous benefits indeed in order to justify these outlays.  Of course, one expects the main benefit of express train service to take the form of reduced Trip Time.
What are the real payoffs attributable to express service?