>No - subway trains can travel 50 mph or more - a bus can’t do that on city centre roads.

If you have really comprehensive coverage in a densely built area you'd be stopping too often for those top speeds to matter.

This is the problem with the Acela. It can technically go up to 150mph, but it has to stop so often that it averages 60mph for the journey.

For longer distances with limited stops, the speed and shigh capacity of a train are good. But to really fill out coverage in a dense area, short wait times and short distances between stops and destinations should be your chief considerations. Buses and streetcars just do that better. Though really, once you get past a certain level of density you need all of the above.

In theory, but NYCs rarely go that fast. This is changing though. I saw a news article recently about how they are lifting the speed limits on some sections of track as repaired signals come online.

Though this probably counts as rarely, least some of the trunk line I've been on give the illusion of high-ish speeds. Examples: - Queens Blvd express (Forest Hills to Roosevelt Ave, Roosevelt to 36 St) - 7 Ave IRT express (from far downtown to 96th St) - Lexington express (City Hall to 125th, save for going through the switches south of 42nd St)

The DC Metro averages 33 mph, including stops. I’d be surprised if NYC’s express lines didn’t hit 50 routinely.

They do not, the max speed limits on rare long stretches of track are around 45 mph. Most stretches are well below this.

https://ny.curbed.com/2018/12/19/18146933/mta-new-york-subwa...

It is worth noting that NYC and DC have fundamentally different design philosophies that result in different average speeds.

New York's system is designed around walking to stations. All the way to the end of the lines, stations tend to be about a half mile apart. There are express lines but even those become locals on at least one end, with half-mile stop spacing.

DC's is an auto-oriented system, where you're expected to drive to the stop and then take the train in from the suburbs. As a result, while there is dense stop spacing in the center, distances between stations in the suburbs get progressively longer and longer. It's over these long stretches in the suburbs that DC is able to attain much higher speeds.