When New York’s Metropolitan Transportation Authority recently released its annual ridership figures, a lot of noise was made about the fact that the MTA has reached its highest ridership in over half a century. At its peak in 2014, New York’s subway system was moving 6 million people every business day . The last time subway moved that many people was in the years immediately after World War II.

As expected, the sharpest increases in demand for the subway were from areas of Brooklyn that are seeing rapid residential growth, such as Bushwick. But growing ridership was spread across all boroughs.

More notable than locations of spurts of growth on the subway are the times of day that have seen the most growth. The subway is experiencing record ridership outside the traditional morning and evening rush hour. More people than ever before are traveling within the city in the middle of the day and late at night.

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The problem for the MTA is that those times are when it has traditionally scheduled its track repair and maintenance. Doing maintenance at those times now causes delays and inconveniences for a huge number of people who rely on the subway system beyond the conventional work day.

‘“The renaissance of the New York City subway is a miracle for those who remember the decrepit system of the 1970s and the 1980s,” said MTA Chairman and CEO Thomas Prendergast, in a statement. “But moving more than six million customers a day means even minor disruptions now can create major delays.”

The changing nature of work is an emerging problem the MTA is going to have to keep dealing with. More people are freelancing than ever before, darting from meeting to meeting at all hours of the day. As companies prioritize output over face-time, people are working at home in the mornings and coming into the office in the afternoons. And the city’s growing population of young people means stops, especially in parts of Brooklyn, are overcrowded late at night and on weekends. Then there’s the part of the New York’s population that has always worked odd or long hours, making the famous city’s 24-hour scene possible.

The MTA is investing in technical solutions that they believe will decrease delays and make maintenance go more smoothly. But meanwhile, New Yorkers are staring down fare hikes every couple of years for a system they continue to experience as not working very well.