Beijing's transport authority has warned commuters to expect even more gridlock in the coming days, as millions hit the road, heading both into and out of the capital, for the holidays.
According to the Traffic Performance Index, which measures congestion on a scale of zero (smooth) to 10 (snarled), the city hit 8.5 during the evening rush hour on Wednesday and 9.1 on roads within Third Ring Road at 7 pm.
Speeds dropped to 20 km an hour for most drivers, the Beijing Municipal Commission of Transport said.
The worst traffic of the year so far, however, happened on Tuesday night, when the index reached a peak of 9.8. By 6:30 pm that day, vehicles were crawling along in the rain at just 13 km/h.
Motorists and bus passengers are being told to expect more of the same.
The capital will see "serious and widespread gridlock" on Thursday and Friday, the commission warned on its website.
Mid-Autumn Festival, which falls on the 15th day of the eighth lunar month (Sept 30 this year), is a traditional time for family reunions, while the National Day holiday, which begins on every Oct 1, is a major travel season.
With the two taking place on back-to-back days this year, the capital has seen an unusual surge in inbound and outbound traffic.
"A major cause of congestion is that cars from all over the country are heading to Beijing several days before Mid-Autumn Festival," said Wang Mengshu, a member of the Chinese Academy of Engineering and a leading expert in tunnels and underground engineering.
The festival has also become an opportunity for people to deliver gifts to maintain connections.
"Every year before Mid-Autumn Festival and Spring Festival (Chinese New Year), we see a sudden increase in cars running on Beijing's streets with license plates registered in other areas. They seize the opportunity to deliver gifts to officials," Wang said.
"Many people from elsewhere in China are not familiar with the road network in Beijing and make wrong turns, which makes traffic even worse," he said, adding: "I don't think congestion in Beijing or other large cities can be eased ahead of such festivals."
The capital's cabbies also have reason to grumble.
When a China Daily reporter took a taxi on Tuesday from Tian'anmen Square to North Fourth Ring Road, driver Wang Shuo'an opted for secondary roads to avoid waiting in traffic.
"I can't believe such a short distance needs so much time," he said shortly after pulling away. His previous fare, from Hepingmen, 3 km away in Xicheng district, took him more than 30 minutes, instead of the usual 10.
"This traffic is too terrible to bear. The most jammed area is Third Ring Road. It's like a big car lot," he said.
Things are so bad, the driver said, adding that he was considering not driving again before the holidays.
Beijing's transport commission has called on people to use public transportation. But the subways and buses also have been affected.
Shao Yu, 24, who works for a media company by East Third Ring Road, said she can not leave her office until 10 pm on Tuesday.
"The traffic jam was so terrible. I took a bus on my way to the office in the morning, but it moved only 1 km in 30 minutes," she said, adding that she had to change to the subway to get to work on time. "The metro is so crowded, too. I don't know what to do."
Vehicles in Beijing surpassed 5 million at the beginning of this year.
To cope with congestion, authorities have taken various measurers, such as introducing the so-called license-plate lottery to limit the number of new cars to 20,000 a month. The city is also considering congestion fees, according to its five-year plan (2011-15).
The number of parking spaces increased by more than 46,000 this year, while the first batch of 2,000 rental bicycles for the public began to appear on the streets in June.
According to the transport commission, another 5,000 rental bikes will be put into service early next month, with the eventual goal to have 50,000 of them.
Beijing is also working to expand its subway network to 440 km this year, comparable with metropolises such as London.
Wang Mengshu, at the Chinese Academy of Engineering, said it is important to build public facilities such as schools and hospitals along the subway to encourage the use of public transportation.
"Nowadays, people live very far away from their workplaces, which wastes much time on the road, and this is a major cause of congestion," he said. "The government should take a leading role to encourage settlements near workplaces, as was done in the past, to ease the worsening traffic.
"Achieving this will harm the interests of property developers, but it's necessary if we want to solve the problem at its root."