RTD’s A Line train to the airport and its crossing gates aren’t working as they should, say federal regulators, and they’re willing to shut it down if necessary.

Regulators said so in a letter to the Regional Transportation District and Denver Transit Partners, the private venture that runs the A Line.

The Federal Railroad Administration has threatened to shut down Denver’s A Line because of what it calls “noncompliance” with national standards.

The FRA said RTD’s failure to improve the timing of its crossing gates is “unacceptable” — a complaint RTD has heard before. The letter was posted publicly on the FRA document database this week.

The timing of the crossing gates have been at issue since the A Line began operating in 2016.

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