The MTA has made good on its promise to install platform countdown clocks at all 471 of its subway stations by the end of 2017 but how well they actually work is now the question that is being raised.

According to the New York Post, a good portion of subway signs are inaccurate, displaying arrival times that don’t reflect the actual times that trains show up. Some stations also have countdown clocks placed in highly inconvenient locations where visibility is impeded, either by another sign or just due to a crummy spot, like the very far end of the platform, for example.

In one instance, a Post reporter found that arrival estimates randomly changed times, jumping from 19 minutes to 10 minutes while in another example, a train arrived before it even showed up on the countdown clock.

MTA officials say that the countdown clocks are continuously being tested in an effort to make them more accurate and that overall, the majority of new clocks are performing well.