It must be the highest traffic jam in the world. It's gridlock on Highway 318 at over 4000 metres above sea level (pictured above), just outside the Tibetan border town of Litang. In a two-kilometre tailback, trucks, buses and Landcruisers sit idling for hours on the main Sichuan-to-Tibet road as work crews upgrade the steep switchback dirt trail into a two-lane tarmac highway. The work is long overdue to cope with the huge increase in traffic to Tibet as "Shangri-La" experiences a boom in tourism and construction. The road starts in Kangding, the traditional border town between the Han Chinese lowlands of Sichuan and the Tibetan plateau. This used to be known as the "Tea Horse Trail", along which heavy loads of tea were carried up by porters to be traded for Tibetan furs and wool. Nowadays, you’re more likely to see Tibetan traders browsing in Jeans West or sizing up the latest iPhones in Kangding’s Apple store. Tea is still traded here, but mochas and fruit smoothies are now the preferred beverage for many young Tibetans. On the surface, race relations seem good despite recent "disturbances" and self-immolations by Tibetans in the Garze district. Han Chinese and Tibetans mingle on Kangding town square every evening, dancing to traditional folk music played on a huge public video screen. At the nearby Anjue Buddhist monastery, authorities tolerate a large portrait of the Dalai Lama, around which local Tibetans have placed prayer candles and wads of Renminbi. Young Tibetans are avid watchers of Chinese soaps on TV. Below the surface, however, tensions remain. Scuffles break out on the street between Tibetan taxi drivers and municipal government inspectors, swiftly drawing hostile crowds. A brittle calm is restored after police haul the offenders away in a van.