BEIJING, Sept. 4 (UPI) -- Poor traffic management and road design are responsible for a massive traffic jam involving more than 10,000 trucks in China, officials say.

Friday's traffic jam is the latest in a series of incidents plaguing the nation's inadequate highways, China Daily said Saturday.

The latest traffic jam extended more than 60 miles, as trucks carrying coal from Inner Mongolia moved bumper-to-bumper along the Beijing-Tibet highway Friday.

The highway has had huge traffic jams a least three times in the past two weeks -- the largest occurred on Aug. 14 and lasted nine days.

Authorities said maintenance work and an exceptionally large number of heavy trucks on the road caused the latest blockage. Production at coal mines in Mongolia is up more than 18 percent over last year, putting more heavy trucks on the road.

Expansion of the country's railroad lines could ease the problem, but there is no short-term solution, an economic expert said.

"Now the country's economy is heavily dependent on coal, and the supply chain of coal is overloaded. Adjusting the industrial structure will make the consumption of coal more reasonable," said Ou Guoli, a professor at the School of Economics and Management at Beijing Jiaotong University.

He said rail is the best method for transporting coal and trains could carry larger amounts more cheaply than surface transportation