Passengers board and leave an A Line train at Central Park station in Denver on Monday, March 26, 2018.

(Nathaniel Minor/CPR News)

The Regional Transportation District is pointing to high-rise growth in downtown Denver as one of the main causes of the district's ongoing issues with the metro area's commuter rail network.

That discovery came in an action plan the district submitted to federal regulators Friday and made public Monday. The document says GPS signals the system relies on to keep the A Line running smoothly and safely are blocked by downtown's skyscrapers.

A software patch for the issue is coming soon according to the plan, along with solutions to other factors affecting the crossing gates.

RTD says it is ready to open the long-delayed G Line to Denver's western suburbs in the first quarter of 2019 if the Federal Railroad Administration accepts its action plan.