Originally Posted by
jackal
Marais pretty much answered your question. Metro North isn't terribly motivated to spend the money required to upgrade the infrastructure to Acela's full capabilities, since its trains can't really use those improvements. In fact, their current track could probably handle higher speeds than the (IIRC) 75mph (or maybe it's 90mph) they limit the trains to, but, as someone around here put it once, MN doesn't want Acelas whizzing by the comparatively slow MN commuter trains filled with rich Connecticut businessmen... (The real reason probably has more to do with fitting the faster trains into available slots without making the MN trains wait any longer than they already do--MN obviously wants their trains to have priority.)
Partly true (although I am not totally au fait with the particular dynamics of this corriddor, I am just speaking of general principles).
Mixing slow and fast trains reduces line capacity. A fast train utilises multiple paths on a predominately slow line, likewise a slow train utilises multiple paths ona predominately fast line. The best way to maximise capacity is to have a fairly consitent speed profile.
This is one of the reasons whay you see Paris and Brussels trains follow each other through the Channel Tunnel, to reduce the effect of faster trains on an otherwise slow sector.
Dave