If your commute has been anything like mine this week, you are probably getting very well acquainted with your fellow Blue Line passengers as you pack into Metro cars. While 12 minute trains with perfect spacing would be at or above peak capacity, it has been clear this week that these problems are magnified by trains running behind (or ahead of) schedule.
The Blue Line carries just under 3,900 riders through Foggy Bottom per hour during Rush Hour. Even if they all show up evenly spaced through the hour (they don’t there are clumps around when people leave work), that is 64 people per minute arriving at stations wanting to board the Blue Line. We’ll assume that some riders switch to Yellow or stop taking Metro altogether because of the cuts and call it 60 riders per minute.
At that pace, after 12 minutes 720 people will be taking the train – which is a full, but not overcrowded, 90 people per car on an 8 car train (Metro’s goal is 80 to 100 per train).
However, there are two problems. The first is that half of the Blue Line trains have only 6-cars, not 8. With just 6 cars, those 720 people will be packed tightly at 120 people per car. As The Washington Post’s Dr. Gridlock pointed out, this alone causes overcrowded cars – especially since riders won’t want to wait 12 minutes in the hopes of getting a less crowded train.
But it gets even worse because Metro trains often aren’t evenly spaced. Metro considers trains on-time if they are within 2 minutes of the expected spacing. But if a 6-car train is just one-minute behind schedule – arriving 13 minutes after the previous train – it will need to carry 130 passengers instead of 120. Two minutes late creates a very cozy 140 passengers per car, even though the train is still technically on-time by Metro’s standards.
When a 6-car Blue Line train arrives just 3 minutes late (a 15 minute gap), the train will now be 50% overcrowded, as 150 people try to squeeze onto each car. This inevitably means passengers get stranded on the platform, waiting about 12 minutes for the next train.
This isn’t just a problem with late trains either. If a train arrives slightly too soon, it will result in equivalent overcrowding on the next train.
These late train problems are real – and routine. During the afternoon Rush Hour yesterday, data received from Metro by NPR’s Martin Di Caro showed that only 2 of the 9 gaps between Blue Line trains were 12 minutes or less. However, Metro’s generous definition of on-time considered all but one train “on-time” so the commute was in-line with an average day. Unfortunately, the combination of poorly spaced trains and 12 minute headway can quickly turn a bad commute into a terrible one. And unless Metro suddenly finds a way to make the trains run precisely on time, it isn’t a problem that will go away any time soon.