Trains per hour vs. minutes per train

Metro is starting to seriously push the Silver Line rollout.  When doing so, they like to tout the number of riders who are helped and hurt by various changes.  But it is not just the number of riders on each side of the ledger that matters.  What also matters is how much they are impacted.  This is where the Metro system’s skewed distribution of trains between Blue and Orange becomes problematic.

Under their old distribution of cars through the Rosslyn tunnel, there were 16 Orange Line trains and 10 Blue Line trains.  This works out to one Blue train every 6 minutes and one Orange train every 3 minutes, 45 seconds.

Switching 3 of the Blue Line trains to Orange (so 19 Orange trains total) means that Orange trains come every 3 minutes 9 seconds.  A time savings of 36 seconds for the Orange riders.

So what did the Blue Line riders give up?  Since they already had less trains, the loss of three more is much more painful.  The average Blue line wait increased from 6 minutes to 8 minutes, 34 seconds.  So every Blue Line rider loses on average 2 minutes 34 seconds compared to the old allocation. Ouch!

But wait, it gets even worse when WMATA plans to move two more lines over to the Silver/Orange corridor.  Now, with 21 trains per hour heading towards Falls Church, the average wait for a Silver/Orange train is 2 minutes 51 seconds.  A gain of a whopping 18 seconds for these riders.

Blue line riders on the other hand will now be up to a 12 minute wait.  So to save riders taking the Orange /SilverLine 18 seconds, Metro is asking riders of the Blue line to give up another 3 minutes 26 seconds for each trip.  This certainly doesn’t sound like a good trade.

Posted in Data, Wait times

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