A road expansion project in north China's Inner Mongolia Autonomous Region started Wednesday, in a step to ease traffic congestion on the freeway between Beijing and Tibet.

A 217-km-long stretch of the freeway between the regional capital, Hohhot, and Baotou City will be widened from four lanes to eight, said Gao Tuanshan, deputy general manager of the Inner Mongolia Highway Construction and Development Corporation.

Construction is scheduled to take two years and the total investment of the project is estimated at 10 billion yuan (1.5 billion U.S. dollars), Gao said.

The Hohhot-Baotou highway section is a trunk line in Inner Mongolia and is shared with the Beijing-Tibet freeway and the Beijing-Xinjiang freeway.

This year, bumper-to-bumper traffic on the section has been a common sight as the number of trucks transporting coal has increased.

As a major coal-producing area, Inner Mongolia has witnessed increased coal output. Transportation of coal by truck in the region surged 49 percent year on year to 50 million tonnes in the first nine months of the year, according to the regional coal mine safety department.

The worst congestion occurred in early September, when a traffic jam lasted for more than ten days when traffic banked up 180 km.

Once the road-widening project is complete, maximum traffic flow on the section will increase to 93,000 units of vehicles per day, compared with the current 40,000 units per day.