No one is more eager than Zeng Shuangquan to see the construction of a tunnel that will cut through Trola Mountain in southwestern Sichuan Province.

As a road maintenance worker at the Trola Mountain section of the Sichuan-Tibet Highway, Zeng and his workmates have to endure extremely harsh conditions at an altitude above 5,000 meters year round.

Zeng's dream is turning into reality. On Wednesday, construction of the tunnel began with an investment of 1.12 billion yuan.

At an altitude of about 4,300 meters, Trola Mountain tunnel will be the world's highest on a highway.

As part of the Sichuan-Tibet Highway that links Chengdu, Sichuan in the east with Lhasa, Tibet in the west, the 7-kilometer tunnel will shorten travel time across the mountain from more than two hours to about 10 minutes, said construction manager Li Ming.

More importantly, it will dramatically reduce the danger for truck drivers zigzagging up and down the mountain, Li said.

The 2,415-kilometer Sichuan-Tibet Highway is one the world's most deadly road as it traverses a dozen rivers and 14 mountains with altitudes of 4,000 to 5,000 meters.

And the Trola Mountain section is considered the most hazardous section of the highway.

Drivers say crossing the snow-covered Trola Mountain in winter is like going through the hell.

Wrecked vehicles lie scattered along the road. On March 14, a bus veered off the road, killing 16 people and injuring 21 others.

Also, the traffic and road conditions have stifled economic development for a large part of the remote mountainous region.

The government began upgrading the highway in 1990 with an initial investment of 1 billion yuan (154 million U.S. dollars) and progress has come.

It used to take about one week in the 1980s to drive from Chengdu to Qamdo County in Tibet. Now it takes two and a half days.

China has spent nearly 140 billion yuan on development of 188 key projects in Tibet between 2005 and 2010, and key among them are projects that link Tibet to the rest of China.

And the governments of Sichuan and Tibet are planning to build more tunnels on several key mountains to improve traffic.

Construction workers are now working on a 14-kilometer approach on the east side of the Trola Mountain to deliver machines and materials for the drilling of the tunnel.

Zeng must wait another four years before the tunnel is completed

He took over the job 10 years ago from his father, who died in his 50s as a result of decades of arduous work at high altitudes.

"I wish the tunnel could open sooner." Zeng said. "Then I could get off this mountain and perhaps regain my health."