A smoky trash fire this month on a stretch of subway tracks in Harlem trapped hundreds of passengers on stalled trains and created a torrent of rush-hour delays across much of the underground system. It did another thing as well: It showed that, sometimes, New York riders are their own worst enemies.

The trash did not deposit itself on the tracks. Somebody — many somebodies — tossed it there. And the all-too-frequent results of this are track fires ignited by sparks from train wheels, which can lead to sudden halts in service that deepen the misery for thousands of riders.

The Metropolitan Transportation Authority has counted 698 track fires since July 2016. That’s arguably not bad compared with the 5,800 fires that the M.T.A. recorded back in 1981, when the subways were at their nadir. Still, it means an average of nearly two such fires a day, each with a potential for dire consequences.

Transit officials could be doing much more to ensure that trash is removed. (Not that we’re counting, but the short stretch of rail that is Track 1 on the Times Square end of the shuttle to Grand Central was littered the other day with no fewer than 47 bottles and cans, and wrappers of all sorts.) The M.T.A.’s new chairman, Joseph Lhota, promises a more intensive cleanup, with the planned purchase of additional high-power vacuums. Mr. Lhota has also raised the possibility of banning the consumption of certain foods on trains, an idea still in gestation.