My source is a detailed and pictured book on Central Asia I read recently, Silk Road to Ruins, written by Ted Rall. China and Pakistan are deserved by a single road, which goes from Kashi to Islambad (capital of Pakistan). This road is extremely dangerous and unreliable, for the following reasons:
- It is going through mountains up to more than 5000 meters of altitude
- The road is closed through the entiere winter and a good part of the autumn and spring
- The road is very narrow at some places, especially on it's Chinese side. It is not possible for vehicles to cross themselves everywhere
- Earthquakes of magnitude 6 or 7 are very common in the area
- Falling stones are common, and they damage the asphalt regularly making huge holes in the middle of the road. Because the place is so remote it's extremely expensive to send trucks and fix the road in order to be safe again
- People tend to drive way too fast compared to what the condition of the asphalt would allow, it is common to see crashed vehicles abandoned down into the ravine
- China drives on the right, but Pakistan drives on the left. People that borrows the road tends to "forget" to drive on the correct side when they are in the other country than their home's.
In addition to those major technical/geographical problems, there is also the political situation to consider, which unfortunately is even more disastrous than the geographical situations:
- The Kashmir region is disputed between India, Pakistan and China. Although the latter two agreed on their borders, India is still claiming the area as a whole. The is occasional clashes and some small wars starts regularly in the area, until they are tired and stop fighting for a while. So you never know when the next wave of violence from either side is coming
- Afghanistan is not far to the road, and terrorist groups from it sometimes take control the area over Pakistani authorities (the author of the book was going to be executed just because he was American, until the events turned into his favour)
- On the China's side, the Turkic Xinjang region as a whole hates the mainland Chinese people as they are severely persecuted by the dictatorial Chinese government. Islam religion is forbidden, mosques are destroyed, and the Chinese authorities force people to eat on Ramadan or to eat pork. Uygur people would take any occasion to get independence over China and expel ethnic Chinese if there was an opportunity, using violence if necessary. The only reason they ceased uprisings is because all the numerous uprisings were a failure, resulting in Chinese killing innocents for no other reason than them being Uygur, and settle even more Chineese colons from mainland.
So no, the Pakistani-Chinese corridor is as unsafe as it could be, and probably will remain.