The Metropolitan Transportation Authority is now testing the software on subway countdown clocks.
Riders say they're showing inaccurate information, especially on the lettered lines.
Trains use beacons and Wi-Fi to communicate estimated arrival times.
The agency says it tested the system on eight lines last year, and found it was 97 percent accurate.
But people who spoke with NY1 feel otherwise.
"I have an app, but sometimes the service doesn't go accordingly. So at least I can look at the time and at least time manage better," said one rider.
"They are really inaccurate. Most of the time it's not what you expect. You have to expect to depart really early, like 15-20 minutes early," noted another rider.
The MTA says it's constantly making upgrades to the countdown software.
The clocks should be in all subway stations by the end of the year.