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Wednesday, December 12, 2018

Speeds Finally Increasing on the NYC Subway

We might have a first here as the increasingly dismal performance of a transit system has managed to override the calls of the safety scolds and the NYC Subway is reversing decades of policy by dramatically increasing speeds system-wide.  Basically someone noticed that when trains run slower, capacity and delay recovery get worse and after trying to shrug things off and claim the cause was a lack of funding, Also we need to credit the role of the media in calling the TA out on it's decades long policy of slowing the system down.

Before you assume that this is only saving time around the margins, just look at the savings in the above chart and remember that this is only the start of the improvements and also doesn't count all of the faulty time signals that are being repaired.  At speeds under 40 or 50 mph, small improvements from 15 to 25mph represent a significant percentage increase in the overall speed.  Going from 10 to 20mph decreases travel time BY HALF, even though the increase is only 10mph.


Let's just go over again why the TA is in this situation.  First, at some point emergency braking rates were reduced to prevent passenger injury on board trains and after some accidents in the 90's, speeds were generally slowed to prevent accidents.  That's legitimate (although the passenger injury thing is less so), however we don't know how this was carried out, especially if it was done without analysis or under existing infrastructure constraints.  Since the 90's slow downs, more speed control mechanisms have been installed.  In some cases it was strictly to reduce wear and tear on curves or prevent other maintenance issues.  In others it was a ploy to decrease reliance on employee skill to maintain a schedule and prevent rulebook slowdowns.


Ultimately the biggest problem is the propensity of rail transit speed restrictions to be sticky. It is always more of a problem to try and change something that has been there for decades, than it is to just leave it alone.  Also, raising speeds requires careful analysis, lowering them generally doesn't.  A speed limit set in 1930 reflected the equipment of the day and was likely very conservative as analysis tools were limited.  Over time employees would learn what the safe speeds actually were,but when decision were made to enforce the limits, the 1930's figures were taken as gospel resulting in unnecessary slowdown.  Currently PTC is bringing the same problem to the national rail system.  I wonder how many decades it will be there is sufficient outcry to reevaluate all of the outdated assumptions that will gum up the works.

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