More than 10,000 vehicles are stuck in a 120km (75-mile) traffic jam on China's Beijing to Tibet motorway.
A state television reporter said the gridlocked section of the road, in the north-eastern region of Inner Mongolia, resembled a "big car park".
The majority of the vehicles stuck in the jam, which began on Tuesday, are coal trucks heading to the capital.
A 100km traffic jam that had lasted nine days on the same motorway was cleared just over a week ago.
The authorities say roadworks are to blame for the latest gridlock.
The motorway is among China's busiest, as Beijing's population of more than 20 million requires massive quantities of goods.
For instance, a huge number of coal lorries have to travel daily from Inner Mongolia in order to ensure a constant supply for the country's coal-burning power plants, which provide more than half of its electricity.
The BBC's Martin Patience in Beijing says that in recent years, there has been a boom in road building across China, with the country spending billions of dollars on improving its infrastructure.
But critics say that China is still struggling to keep up with the demands of its growing economy, and that huge traffic jams could be here to stay.