Construction workers on the Qinghai to Tibet railway are facing some of the most extreme environmental conditions tackled by any railway builders. Work has now been completed on the Hoh Xil plateau, which is up to 4·7 km above sea level, and the next stage of the project will take the railway to an altitude of 4·9 km.

Temperatures can fall to -20íC, and work is only possible during the summer months. The use of oxygen supplies is compulsory, leading Dieter to think there might be an opportunity to establish a chain of oxygen bars along the route of the railway. Because of the extreme conditions, workers’ shifts are limited to 6 h, and special meals are provided.

Despite the unfavourable environment, Hoh Xil is a breeding ground for pantholops hodgsonii, the endangered Tibetan antelope, and in August work on the railway was suspended while the animals migrated.