Originally Posted by
Dr. HFH
While I always liked the express service, I never really got it. If you only have one track in each direction, express service means that the express train has to wait a bit after the last local train before it can leave so that it doesn't catch up to the local ahead of it. So you don't really get to Makkasan or Phaya Thai any more quickly. Or you can have some areas of the track split off into two in each direction so that the express train can pass the local; but that requires very precise timing.
The real way to do express service is to have two tracks in each direction, one dedicated to express service.
This [bolding mine] is exactly how it was set up. Hua Mak was the bypass area and Makkasan's alignment could have allowed the same but the track was never configured to do so.