This is the UP Gila Sub that was once the ex-Southern Pacific Sunset Route that runs 255 miles from Yuma, AZ, to Tuscon, AZ.
Between Dome and Wellton, there is 16 miles of original SP double track. The 2nd track was built in 1926, with the original main built by the end 1879. While it shows 2 main CTC, the trackage is signaled basically in one direction like traditional ABS. Nice old ex-SP cantilever signals are located around Wellton and Dome back in 2017. Changes are on the way as the railroad prepares for the PTC system, these old timers days's are probably numbered.
