An A Line train rests at the Denver International Airport platform on the line's opening day, Friday, April 22, 2016.

(Nathan Heffel/CPR News)

The federal government may soon shut down two commuter train lines in the Denver metro.

Problems with crossing arms have plagued the A Line from Union Station to Denver International Airport and the B line from Union Station to Westminster since they opened. Flaggers, paid for by a Regional Transportation District contractor, have been stationed at the crossings while officials look for a fix.

"They were not running consistently and they weren't staying down at a consistent time," said RTD spokeswoman Tina Jaquez.

The Federal Railroad Administration granted the district a temporary waiver to keep the lines open. But that ends on Nov. 5. 

RTD officials are trying to fix a software issue with the crossing arms. They will meet with federal representatives to try to head off the worst-case scenario: a shut down of the lines.

"It'll really just depend on what they do after [Nov. 5], as far as whether we've got it resolved or they are happy with the resolution that we offer. We kind of just have to wait and see," Jaquez said. "We hope that by meeting with them, and working toward a resolution we can avoid that."

RTD estimates the A Line has 18,000 weekday riders, and the B Line has 1,400 weekday riders. The gate crossing issue has contributed to delays since the A Line opened; RTD says it is on time 87.3 percent of the time. The goal is a 90 percent on-time rate.

In a statement, an FRA spokesperson said RTD needs to demonstrate it has a path forward to a permanent fix.

"While trained flaggers, wearing appropriate personal protective equipment, at every crossing do keep motorists, pedestrians and train passengers safe, this was never meant to be a long-term solution," the statement reads.