The federal agency that oversees railroad safety is threatening to shut down the RTD's A-Line because of a failure to improve how crossing gates operate. In a letter published on the agency's database this week, the Federal Railroad Administration criticized the RTD for failing to meet national standards for crossing gates. After doing some testing of the gates in August, the FRA said the timing on the gates was unacceptable and threatened to shut down the A-Line if something isn't done. The letter also said the FRA would not allow the RTD to open its G-Line from Denver to Wheat Ridge because of its concern over the crossing gates.