During peak hours, according to the City Land Transportation Agency (DLLAJ), only 4 percent of private vehicles carry four passengers or more, and 82 percent only carry between one and two passengers.

And 60 percent to 70 percent of private vehicles and motorcycles exceed emission standards.

"That means there has to be a policy restricting the use of private vehicles," D.A. Rini, the head of DLLAJ's program supervision department, said during a seminar here on Saturday.

But private vehicles are not the only cause of the city's transportation woes, Rini added.

"The transportation problems in the capital are very complex and wide-ranging, and one thing is related to another," she said.

The number of vehicles -- and the distances traveled in them -- is connected to the speed and type of fuel of the vehicles, all of which contribute to and worsen air pollution, she explained.

Every day, Rini said, there are about 16 million people on the move in the city, with 20 percent of them being commuters from Greater Jakarta as more and more residents move to the suburbs.

"As a result, more fuel is needed and chronic traffic jams occur along the roads in the suburbs, especially in the morning and afternoon," she stated.

Traffic jams reduce the speed of vehicles, and the slower the speed the higher the concentration of the hydrocarbon gases and carbon monoxide (CO) emitted by the vehicles.

"Right now, air pollution caused by gasoline is greater than that caused by diesel or car gas, as 99 percent of the vehicles in Jakarta use gasoline," Rini said.

The city is to ban the use of leaded gasoline starting from July 1 in an effort to reduce air pollution.

This, however, is not enough.

According to Rini, the most urgent step is to reduce vehicle density and increase the average vehicle speed on the streets.

"The three-in-one program, where only cars with at least three passengers can travel on main thoroughfares, is good. But it should be optimized as the program only operates between 6:30 a.m. and 10 a.m.," she said.

The next program, she added, should be to arrange the capital's parking system so as to increase revenue, limit unnecessary travel, improve traffic flows, and protect pedestrians and the environment.

"Parking along city arteries should be banned. The collaboration with the private sector in parking should be reviewed," Rini said.

As for traffic, she said there should be more area traffic control systems at junctions which would shorten the length of time vehicles are stopped at them.

Rini also noted that the public transportation system must be improved to reduce the number of private vehicles on the streets.

"Residents and the private sector should also be involved in the program through measures such as expanding the opportunities for owning public transportation companies, providing more auto-repair shops to check vehicle emissions, providing converter kits to enable automobiles to run on car gas, and making vehicles using car gas more widely available," she said.

Meanwhile, the head of the City Environmental Impact Management Agency, Aboejoewono Aboeprajitno, said that starting next year there would be a one-stop system for obtaining drivers' licenses and having vehicle emissions checked.

"So vehicle owners will only be able to receive official permission to use their cars if they pass an emissions test at a licensed auto-repair shop," he said.

The Japan International Cooperation Agency announced in 1995 that 71 percent of air pollutants in the capital came from motorized vehicles, of which there were 3.87 million, with this figure growing annually by 9.77 percent.