Residents of the west Denver suburbs will notice more trains on the tracks for RTD’s yet-to-open G-line beginning Thursday as the transit district moves into the next phase of testing.

The commuter rail line, which will provide service from downtown Denver to Arvada, Wheat Ridge and parts of Adams County, has now been federally approved to carry six trains for up to 10 hours a day, RTD said in a news release. The trains will run along the 11.2-mile train line roughly every 15 minutes between 3 a.m. and 1 p.m., according to RTD.

The new testing doubles the amount of trains and the frequency with which they run over the previous phase that began July 20. The district is ramping up to a full service day’s worth of testing, a period of 21 consecutive hours.

The public is asked to abide by proper safety protocols around the tracks.

The G-line was originally expected to open in fall 2016 but safety concerns have repeatedly delayed it. There is no firm opening date now planned.