Bad weather tends to go hand in hand with longer Metrorail delays. Delays usually last the longest when it’s freezing outside, with the situation being a bit better when it’s snowing and even better when it’s only raining.
Between January 2013 and January 2017, there was some kind of Metrorail delay virtually every day; nearly 20% of Metro trains arrived late in 2016. That may sound alarming, and it’s certainly bothersome, but Metro isn’t alone when it comes to delays being part of a standard day: in New York City, for example, 25% of subway trains were late every day in 2014. And like with Metro, the situation in New York isn’t getting any better as delays have increased over 150% for NYC buses and subway trains over the last four years.
While there is a delay just about every day, the length of the delay really ranges. We recently dug into 604 days’ worth of data on inclement weather between January 2013 and January 2017, looking at how bad weather tends to impact Metro delay times.
While we can’t say that bad weather caused the corresponding delay times, we certainly can observe the correlation between bad weather and changes in delay times.
First, let’s look at the baseline
From January 2013 to January 2017, the average Metrorail delay was between six and eight minutes long; delays fell into that time window 45% of the time.
Image made by the author, using the Keshif data explorer.
The second most common delay time over the last four years was between eight and 10 minutes. 27% of waits were that long, meaning that just about 75% of all delays between 2013 and 2017 were 6-10 minutes in length.
Knowing the average for all delays, it stands to reason that the frequency and length would differ for days with inclement weather. In the chart below, the top row shows the same information as the graph above while the three rows below it show the average daily Metrorail delay time during freezing temperatures, snow, and rain.
The middle black lines show the median of the daily averages for each weather type, and lines on left/right show percentile ranges.
As you can see, delays were relatively higher when it was freezing (red row) compared to the typical (all conditions, top row).
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