The Subway: Mean Distance Between Failures Falling, So Is the 1980s Returning?

In the 1990s there was an improving statistic that was as central to New York City’s turnaround as the decrease in the crime rate: the increase in mean distance between failures (MDBF) on the New York City subway. This figure, which measures how long the average subway car goes before it breaks down in service, is considered a key measure of the overall health of a railroad.

In any statistic there are random variations, in part due to temporary unusual conditions. That’s why a one-month increase or decrease in the crime rate, compared with a year earlier, or a one-year increase or decrease in school test scores, doesn’t really mean much. Once a trend is really established, however, it ought to be news. Which is why I was shocked to find, in the MTA Board materials, that MDBF has been falling for three years, not on a one-month basis but on a 12 month moving average basis. The decrease is now significant enough to affect service as people experience it, and may mark the start of a significant downward spiral for the system.

I was shocked because unlike any uptick in the crime rate, this negative trend has not been widely reported. It is shown without comment in Chart 10 of the most recent Board Meeting materials for the Subway and Bus committee, on page 29.

“MDBF in May 2016 decreased 13.3% from May 2015. Over the past year, the MDBF 12-month average decreased 15.3%.”

With ridership falling as well, and revenues coming in below budget, one might imagine that years of financial decline are finally manifesting themselves physically.

While the MTA is not exactly issuing press releases highlighting these negative trends, it isn’t exactly covering them up either. They are right there in the board materials. So it would appear that no one in the media actually takes the time to read through MTA documents looking for news. Either that or because those who ride the subway are considered serfs, what happens to them or the system is not thought of as news. Particularly if it happens slowly over time.

Then too if the subway has returned to deferred maintenance, virtually every politician and interest group active in New York has a hand in the blame. Like the financial impact of all the retroactive pension increases on the NYC schools, the impact of the MTA debt on subway service may be under Omerta. So no one issues a press release to form the basis of a new story. Meanwhile, Mayor DeBlasio’s political enemies highlight any short-term increase in the crime rate.

Measured on a 12 month moving average basis, this decrease in subway reliability is not short term.  Alarmed, I went back and looked at the oldest subway and bus committee board materials on the MTA website, from October 2015, and went straight to Chart 10 on page 27.

The chart shows that while MDBF was stable from October 2014 to October 2015, it was down significantly from around 160,000 miles between failures in August 2013. After leveling off for a while it is falling again, to just over 120,000. That’s getting close to a 25 percent decrease in reliability. For those who remember what subway travel was like when MDBF was down around 30,000, this trend is a nightmare.

It was not long ago that the improvement in MDBF was a point of pride for the MTA, and the subject of repeated newspaper articles and radio and TV pieces, just like the decrease in the crime rate. The improvement was explained – union workers (finally) doing their job, better training, improved management, scheduled maintenance rather than waiting for the trains to break down on the road, new and overhauled subway cars.

What is the explanation now? Tables show that MDBF is falling for new and older cars alike.