The New York City Comptroller's office says the railroad's delays and cancellations inconvenienced more than nine million riders.
The problems caused about $75 million in lost productivity, the report found.
In January of this year, the LIRR's on-time performance was 83.9 percent, a 22 year low. Bad weather was a contributing factor.
The Metropolitan Transportation Authority says it has heard its customers "loud and clear" and is taking a "host of aggressive actions" to improve service.
They include adding staff; seeking ways to reduce weather-related delays; and upgrading signals, switches, tracks and crossings.
(The Associated Press contributed to this report.)
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