KUSA — Ramped up testing started on RTD's G Line on Thursday morning after the Federal Railroad Administration approved testing in mid-July.

They're now allowed to run as many as six trains on the G Line for 10 hours each day – every 15 minutes, between 3 a.m. and 1 p.m.

Eventually RTD hopes to simulate the full daily service schedule of nearly 21 consecutive hours. The official start to that next phase of testing has not been announced, and an opening date for the G Line has not yet been determined.

Limited testing on the G Line began last fall, and has been underway weekdays from 8 a.m. to 6 p.m. since the start of the year. The line will run 11.2 miles from Union Station in Denver through Adams County, Arvada and into Wheat Ridge.

“We are excited to see G Line testing ramping up,” RTD CEO and General Manager Dave Genova said in a news release. “Safety remains crucial during this time, and while we know that people are as excited as we are to see many trains on the alignment, we ask that they keep an appropriate distance and respect the work taking place on their behalf."

RTD has been trying to resolve issues with crossing warning times on the A Line to align with state and federal regulators, and the 16 crossings on the G Line use the same technology. The G Line was originally slated to open in the fall of 2016.

Starting July 20, up to three trains have been tested every day at half-hour intervals starting as early as 3:30 a.m. and extending through 1 a.m. the following day.

Train operators will continue to use their horns while passing through intersections to make sure drivers and pedestrians are aware of train movements. Quiet zones for the G Line will eventually be put into place once approvals from the FRA are in place.

When the G Line eventually opens, trains will run every 15 minutes from 6 a.m. and 6:30 p.m. and every 30 minutes during non-peak hours.

PREVIOUS G LINE COVERAGE:

When’s the G Line opening?

Does A Line’s recent approval help G Line?

The G Line: Arvada's unicorn

Olde Town Arvada businesses adapt to life without G Line

RTD gets a 5-year waiver from federal railroad standards

RTD floats idea that it could run the yet-to-start rail service to Thornton itself

RTD G Line testing resumes

RTD gets second chance to prove A Line crossings are safe, and the guards can go

RTD request for flexible crossing times denied, rail lines will still need crossing guards