SHANGHAI, China — When word got out two weeks ago about China's monster traffic jam, an amazing thing happened: drivers continued to willingly flock to the Beijing-Tibet expressway at the heart of the problem.

Why? One driver in the middle of the miles-long string of cars said it best: “Everybody has to use this road as the other is too expensive,” he told Guardian.

What it comes down to is tolls, say drivers, and the fact that they cost too much. The Chinese government has greatly expanded the network of roads, but most new roads operate via a toll system that, quite frankly, people will do anything to steer clear of.

As the infamous story of the world's largest traffic jam fades into the background — and the expressway that became known as a parking lot, chess club and unisex toilet, finally returns to its intended purpose — many worry that more massive traffic jams will follow.

Experts say it's possible, and if this past weekend's news is any indication (China's massive traffic jam made a slight reprise Saturday), it may even be likely.

“Although such large-scale gridlock is exceptional, traffic jams that are measured by days are not rare in China," said John Zeng, auto analyst at global marketing firm J.D. Power and Associates, adding they will be "hard to avoid in the future.”

Many have attributed the cause of the mid-August monster traffic jam, which lasted for 10 days and reached 60 miles long at one point, to road construction on a road that carries tens of thousands of vehicles everyday.

Others say the main problem is that China doesn't have enough roads for its intensive cargo transport. As its rail transport struggles to serve the country's 1.3 billion people, China's road system has to answer most of the nation's logistics demand. In addition, an increasing number of Chinese started purchasing private cars, creating more pressure on the roads.

But, by any measure, China's road system is impressive. Official statistics show that expressways reached over 40,000 miles in 2010 — a roughly four-fold increase since 2000. In the next two or three years, China is expected to bypass the United States as the country with the largest expressway system.

If the problem is costly tolls, which drivers say it is, then it doesn't matter how many new roads there are, the traffic jams will persist.

According to a 2008 World Bank report, the toll per mile in China is the same as in the U.S., where the GDP per capita is roughly 15 times greater. Thus, relatively speaking, Chinese tolls are the highest in the world.

The fact that few drivers were willing to seek alternative roads to the Beijing-Tibet expressway during the height of August's jam is perhaps the most convincing evidence of this phenomenon.

But in other parts of the country, drivers complain of the same problem. Wang, a 46-year-old truck driver who asked to go only by his last name, delivers rice from north China to a coastal province around 800 miles south. He said that more than one-third of his expenses go toward paying toll fees.

To soften the blow, Wang says he looks for the cheapest route, and so do his peers. The roads aren't designed to absorb the heavy traffic flow that results.

In less-developed western China, the picture becomes even clearer.

“Two roads can take you from point A to point B, expensive highways are often seen empty, while nearby roads are completely packed,” Zeng said.

And, even for those who can afford the tolls and do opt for the expressways, the journey isn't smooth.

Unlike in the U.S., where drivers have the option of things like EZ-Pass, which allows an electronic reader to automatically charge the car as it drives through the toll, most Chinese drivers have no choice but to come to a full stop in order to pay their tolls.

“This certainly could impact traffic and create congestion,” said Bob Honea, director of the University of Kansas Transportation Research Institute.

Despite China’s great efforts to improve infrastructure, Shomik Mehndiratta, a senior transport specialist from the World Bank’s Beijing office, said a stronger focus on traffic management is needed.

“China is getting, by and large, the investment side of the logistics done, and perhaps more can be done on coordination, management and getting customer-oriented services,” said Mehndiratta.

The central government appears to be aware of the problem. Beijing has urged local authorities to cut back on tolls gradually. Beijing has also delegated audit committees to rein in overcharge practices at toll booths, and it has started installing electronic readers on major expressways.

But implementation is another matter. As the Chinese saying goes, “the mountains are high and the emperor is far away.” The country’s drivers, like Wang, often find out that the central government’s order is not always working on the local level.

“I was once driving on a road that is regulated as free,” Wang said. “Then, a toll booth that should not exist stopped me and asked for a fee. I told them it isn’t right, but had no choice except paying.”