In conjunction with major ongoing upgrades and expansions being made to the Port of Oakland in order to better accommodate the rapidly growing North American trade with Asia and the Pacific, the cooperation of UP, the Port's principal rail partner, has been sought to construct a second track and raise tunnel clearances over Donner Pass for container trains linking California with the rest of the country. This would likely require either a new parallel tunnel next to Tunnel 41 or the replacement of the summit section of Track 1 between the Norden complex and Shed 47; either would increase capacity and effectively eliminate delays currently caused by having to run all east and west bound traffic between Norden and Shed 47 over a single track. (To fully eliminate bottleneck delays the now single track section between Switch 9 (MP 171.9) at Emigrant Gap and Shed 10 (MP 179.0) west of Cisco would likely also have to be restored to double track.) Improvements were completed on the Sierra grade in November 2009, including increasing of tunnel clearances in 15 restricted tunnels between Rocklin and Truckee and upgrading of signals to CTC, although the original Donner Pass grade (Track 1) was not restored. Since then trains of full-height or , double-stack container cars have run over Donner Pass; some tunnels on Track 2 between Bowman and Colfax were not enlarged, so stack trains in both directions must use the older, tunnel-free Track 1 between those points.