A contractor posted at the A Line crossing at Steele Street in north Denver holds a stop sign on Tuesday, Jan. 24, 2017. The flaggers are required at each grade crossing along the A and B lines until issues with the lines' positive train control system are resolved.

(Nathaniel Minor/CPR News)

Posted 11:30 a.m. | Updated 1:15 p.m.

State regulators denied a request Wednesday from the Regional Transportation District that could have eventually led to the opening of the long-delayed G Line commuter train from Denver to Wheat Ridge and Arvada.

Malfunctioning wireless technology that controls at-grade crossings has plagued RTD’s new commuter rail lines, the A Line to Denver International Airport and the B Line to Westminster. Crossing gate arms sometimes come down too early and go up too late.

The Federal Railroad Administration and the Colorado Public Utilities Commission allowed those two lines to open in 2016 under the condition that flaggers were stationed at each crossing. The opening of the G Line, originally scheduled for last fall, was delayed until the technical problems were sorted out.

RTD says it has made progress in fixing the problem. It asked the Colorado Public Utilities Commission for approval to start full testing of the G Line and to call off the flaggers on the A and B Lines. That approval is a prerequisite for the federal government to sign off on the plan as well.

But PUC commissioners denied RTD’s request. 

"The commission ruled that RTD had not established evidence that the proposed crossing warning times would result in safety for drivers using the crossings," said Terry Bote, a PUC spokesman. 

RTD needs to prove its crossings operate according to the designs the PUC initially approved, Bote said.

An RTD spokesman called the vote "disappointing." 

“We thought we were very close to meeting the requirements as stated," said Scott Reed, assistant general manager at RTD. "But we'll continue to work with the PUC in addressing the concerns they have and making sure we are able to resume testing on the G Line."

Reed said there’s no estimate as to when the G Line will open.