Transit experts say the ongoing troubles plaguing completion of metro Denver’s commuter rail system are among the worst in the country — even as its ridership is growing.

The big sticking point — which has prompted 2 1/2 years of delays and produced dueling lawsuits — is the timing of the safety gates at crossings on the University of Colorado A-Line to the airport and the yet-to-open G-Line to the west suburbs.

Last month, federal regulators demanded that the Regional Transportation District submit a plan by the end of this week that identifies a fix for the issue once and for all — or face the possibility of a shutdown of the 23-mile A-Line.

“It’s in the realm of serious concern,” said Andrew Goetz, a geography professor at the University of Denver who is also a member of the school’s Transportation Institute. “It’s at the far end of the scale in terms of delays.”

But some experts note that the situation, which stems from an unusual collision of an emerging rail technology with new railroad safety protocols mandated by the government, is more complicated than most people realize.

P.S. Sriraj, director of the Urban Transportation Center in Chicago, said that technology-regulatory conflict amounts to something of a “perfect storm” for RTD as it attempts, thus far in vain, to find a remedy to inconsistencies in the timing of the system’s crossing gates.

RTD and its private-sector partner, Denver Transit Partners, claim that their efforts to be the first transit system in the country to combine positive train control with new wireless signaling technology for crossing gates from the ground up is at the heart of the timing problems seen at the crossings, where gates generally stay down longer than Federal Railroad Administration standards require.

“You can get a sense of how uncertain it is to implement a new technology without any hiccups. This is the first time you are seeing a paradigm shift and that is the main cause (of the problems),” Sriraj said. “If it was not RTD, it would have been someone else.”

RTD not alone

Positive train control, or PTC, is a federally mandated safety system designed to reduce crashes and derailments. But its implementation across the country has been far from smooth, and Congress has extended the deadline to activate PTC from the end of 2015 to the end of this year. Additional extensions to the end of 2020 are now likely.

That, said RTD board Chairman Doug Tisdale, is the challenging environment in which his agency is operating.

“We have to develop this without the benefit of the experience of other agencies that have done it,” he said. “We’re the early adopter.”

That adoption process has turned toxic as Denver Transit Partners, a consortium of private companies working on a $2.2 billion, 34-year contract with RTD to build and maintain the A-Line, G-Line and B-Line to Westminster, sued RTD in September. DTP points out that the A-Line and B-Line have safely transported millions of passengers for more than two years and claims the consortium has been wrongfully saddled with the cost — to the tune of “tens of millions of dollars” — of providing human flaggers at crossings as a safety backstop.

RTD responded the following month by telling DTP that its failure to meet gate crossing timing rules set by the federal government and its inability to open the G-Line for passenger service constitutes a “termination event” in the contract between both entities. The A-Line has been in service since April 2016 but operates under a waiver from the Federal Railroad Administration because of the gate issues.

The FRA weighed in last month, warning that regulators could go as far as suspending A-Line service if RTD doesn’t submit a plan that points to a solution to the crossing gate problems. In the letter, FRA’s chief safety officer wrote that RTD’s continued failure to provide warning times at its crossings that are within federally mandated ranges was “unacceptable.”

RTD has until Friday to submit its plan to Washington, D.C.

To be sure, RTD is not the only transit agency to hit hurdles opening or operating a line.

The MBTA in Boston is currently considering whether to continue with Keolis Commuter Services as its commuter rail operator. The system, which serves the city’s suburbs, recently experienced a derailment and an engine fire on two different lines and Keolis was hit with thousands of dollars in fines in 2015 for late trains dogged by blizzards and lightning strikes.

Across the country in California, Sonoma-Marin Area Rail Transit got off to a rocky start in 2016 with a host of problems, including the need to replace the engines on all of its trains. What was supposed to start rolling along a 43-mile stretch between Sonoma and San Rafael in late 2016 didn’t open until the following summer.

In Maryland, the 16-mile Purple Line connecting Bethesda to New Carrollton has generated negative headlines as residents along the route have complained of loud noises and vibrations from construction of the light rail line northeast of D.C.

Christof Spieler, an urban planner and structural engineer who served on the board of directors of Houston’s Metropolitan Transit Authority of Harris County, said the decision of RTD and DTP to play at the cutting edge of rail technology with wireless signaling invited a higher level of risk to the whole process. The contract for the three rail lines, known as the Eagle P3 project, is considered the first public-private partnership on construction of a commuter rail system in the United States.

“It’s pretty common to have the first adoption of something go through a bit of pain debugging it,” Spieler said.

Where’s the expertise?

On the other hand, Spieler and other transit experts are surprised that RTD’s problems center on an element of railroad operations that is nearly as old as parallel tracks.

“One of the things that is unusual is that crossing gates are a very well-known technology,” he said. “The thing that is not working is not the thing you would expect to not work. It’s definitely odd that this hasn’t been resolved after this long.”

Goetz, the DU professor, has a dimmer view of RTD’s efforts to deploy commuter rail. He lobs pointed criticism at Denver Transit Partners, made up of top engineering and construction firms Fluor Corp., John Laing Group, Balfour Beatty Rail, and Ames Construction.

“If they can’t deliver on their tech ability — after all that is one of the main selling points of entering into a public-private partnership — that is a serious concern,” he said. “Is this technology so rigid that once they get locked into a certain threshold, they can’t change it? Shouldn’t your system be robust enough to meet these standards?”

One of the more frequently raised questions is why RTD hasn’t jettisoned wireless technology in favor of proven signaling systems. RTD spokeswoman Laurie Huff said “abandoning the current system would be costly and time-consuming.”

“DTP has told RTD that it believes its signaling system will meet FRA requirements,” she said. “We hope passengers will remain optimistic. RTD is completely focused on doing everything it can to open the G-Line and implement quiet zones as soon as possible.”

John Thompson, DTP’s executive project director, said an “independent review” has determined that abandoning the wireless signaling system at this point would be counterproductive. The technology on the three lines, he said, is “working as designed and intended.”

“Reverting to a traditional system would be complex on an electrified railroad like the A, B and G-Lines and, most significantly, would actually lead to longer and less consistent crossing warning times,” he said.

As frustrating as the delays have been, Sriraj, with the Urban Transportation Center, said the service that’s operating is actually performing very well when measured against national standards. He noted a better than 97 percent on-time rate for the A-Line and a healthy ridership.

Through September of this year, there have been nearly 5.3 million A-Line passengers compared to nearly 4.9 million during the first nine months of 2017, according to RTD — an 8 percent increase.

“I would preach a little more patience,” Sriraj said. “I do think this gets resolved.”