It's also exceptionally important for a spur route, as it traverses all of Tibet, and without it the entire prefectures of Garzê, Nyingchi, Shannan (via G4219), Xigazê and Ngari wouldn't connect to the NTHS system at all.

It is practically an extension of G42, but shares its last two digits with the culturally prestigious[1] China National Highway 318, which parallels it for the Ya'an-Lhatse section, and which in turn is part of AH 42.

Moreover, it does not even connect to G42: the Chengdu-Ya'an section of G5/G93 links them, and together they will create an uninterrupted, non-detouring domestic drive between Shanghai and Kargilik that is over 6,000 km long.

If we can solve the various technical problems regarding this, we would be more than capable to easily handle any other expressway project anywhere else.The Ya'an-Kangding section alone climbs 2,000 m of altitude over its 130 km route.

The Ya'an-Xichang expressway earned the nickname of "the ladder to heaven" for its steepness, but it still pales in comparison to this section.

It's considered at least "extreme on five aspects", namely geography, geology (the region not only being prone to earthquakes, but also difficult to tunnel through), climate, ecology, and engineering challenge.

The Kangding Bypass section encountered hundreds of rock bursts that affected the safety of the project.

[4] Details of people documenting the difficulties encountered in the construction of G4218 is widely available in Chinese but not in other languages.