BEIJING - What is the most lucrative industry in China? The answer lies in selling neither securities nor real estate but in building highways.

Payments of highway and bridge tolls make up as much as a third of the total transport costs incurred by trucking and other types of hauling companies at a time when toll collectors are raking in large profits, according to a report by China Central Television (CCTV).

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The report recounted the experience of a truck driver, Wu Zhongyao, who said he spent 8,978 yuan ($1,382) on tolls in April while making a 2,800-km trip from South China's Guangdong province to Northeast China's Liaoning province. That money made up a third of his total freight expenses, which came to about 27,500 yuan.

Wu said he made a thin profit - about 7,000 yuan - on the trip, which lasted for three days and two nights. And he'll be lucky if he gets to keep most of that.

After he makes payments on truck insurance and bank debt and pays overload fines, his earnings often fall to 2,000 to 3,000 yuan a month.

"Ninety-five percent of cargo trucks must either be overloaded or given extra height to make them profitable or able to compete with rivals," Wu told CCTV.

Travelers have long complained about the collection of heavy tolls along China's highway system. The cost of making extra trips can be so high that truckers and companies find themselves preferring to overload their vehicles or illegally evade tollgates at the risk of incurring fines.

At the end of 2010, a farmer, Shi Jianfeng, in Central China's Henan province received a life sentence for not paying 3.68 million in highway tolls over the course of eight months. The case prompted an outcry online; many people came to Shi's defense, saying the toll cost was exorbitant and far exceeded Shi's annual income.

Industry insiders also blamed heavy tolls as the cause of an apparent discrepancy in the prices of vegetables. Noting that farmers are now suffering because they must sell their vegetables at abnormally low prices, many observers have wondered why the price of vegetables at market hasn't likewise dropped. Experts and government officials have said the discrepancy results from "the high cost of transporting goods".

Dai Dingyi, vice-chairman of the China Federation of Logistics and Purchasing, told CCTV in a previous report that highway and bridge tolls in China are too high for transport companies. Tolls, he estimated, make up as much as 30 percent of such companies' total costs.

Transport authorities in China have taken steps to reduce toll fees. Feng Zhenglin, vice-minister of transport, said during a telephone conference at the end of April that the ministry will study the debts, revenues, and charging practices of toll collectors and will reform or shut down collectors that fail to obey the rules they are subject to.

According to statistics from the Ministry of Transport, tolls have ceased since the end of 2010 to be charged along more than 90,000 kilometers of second-class highways financed by government loans. During the same period, 1,723 tollgates were closed in China.