The holy city on the "roof of the world" is increasingly congested with traffic as more families can afford to buy a car.

"It's a real headache to drive during the rush hours -- sometimes you have to wait 30 minutes at a single crossing," said truck driver Tashi, who, like many Tibetans, goes without a family name.

Tashi travels several times a day between a grocery market near the Potala palace in the heart of Lhasa and a food street in the outer areas, transporting vegetables and other groceries on his pickup.

"It was never congested like this in the past," he said.

Lhasa has more than 100,000 motor vehicles on its 50 km of urban roads. Eighty percent are private cars, according to the city's statistics bureau.

The expanding car fleet is one of the most apparent indicators of local economic growth. Lhasa's GDP has grown by an average 15.5 percent annually to hit 15.43 billion (2.32 billion U.S. dollars) last year.

Last year, the city's average per capita disposable income reached 15,114 yuan.

But too quickly, local drivers are experiencing the headache of being trapped in long queues either to move or to park.

Tsering, who works at Tibet's regional association for the disabled, recalled the frustration of waiting for 30 minutes for a parking space near a fastfood restaurant downtown, where eating took just 20 minutes.

When Lhasa's biggest shopping mall opened on a busy commercial street east of the Potala Palace last Saturday, the area was congested with cars.

"Our parking lot can accommodate 120 cars. At the busiest times, almost 1,000 cars were waiting to park," said a carpark worker.

He said the parking fee was 2 yuan per hour. In big cities like Beijing, however, the price has been raised to 5 yuan an hour in the busy areas to divert traffic flow.

Lhasa Vice Mayor Wang Hui said 54 car parks, with at least 10,000 parking spaces in total, would be built in the next two years to meet growing demand.

Congestion has been a growing concern for Lhasa residents since last year. Kunga Dondrup, an advisor to Tibet's political advisory body, even suggested city authorities restrict traffic through an odd-even license plate system, a move practised in Beijing for more than two years.

"It's necessary to restrict traffic flow and give priority to public transport," he said at an annual political advisory session in Lhasa in February. "The move will ease congestion and cut emissions."

Last year, Lhasa reported 87 deaths on the road, a 13-percent rise year on year.