A Beijing Capital International Airport security officer examines a passenger's luggage, as inspections at the airport and bus stations were increased to ensure safety during the Games. [Xinhua]

At 5 am Sunday, Beijing's sky was clear, and veteran cabbie driver Duan Shitou was pleasantly surprised by the smoothness of traffic.

Even after he had driven for an hour and was approaching Zhaogongkou, one of the capital's busiest long-distance bus stations, the roadway seemed ideal for a Hollywood-style car-chase.

"I've hardly ever felt this good driving here," the 50-year-old said. "The traffic now is like it would be at 4 am on a normal day. We should've adopted this (alternating odd-even license plate policy) long ago."

The policy, which began on Sunday and would last for two months, would not immediately mean better business for cabbies. But in Duan's words: "It feels fantastic to have so many cars off the streets."

However, many newcomers to the city, such as freelance artist Zheng Quan, of Henan province, are not so taken with the policy.

At 7:15 am, the 24-year-old stood alone outside the busy station, staring at a giant, updated map of Beijing.

"I know very little about the odd-even thing. All I know is we went through four checkpoints when the bus got here this morning," Zheng said. "Each one took us 10 minutes."

From Sunday, all buses from the provinces to the capital would undergo security checks at their terminal stations rather than en route to Beijing. But a policeman, who refused to reveal his name, said implementation might take "quite a while" because of heightened security concerns.

"In the past, only those traveling from here to other places needed to undergo security checks. Since July 15, we've started using new checkpoints for visitors to Beijing as well," Zhaogongkou staffer Wu Licheng said, pointing to the "passenger exit & safety check" area - a small makeshift building without a door.

All visitors to Beijing during the Olympic Games must purchase bus and ship tickets using their real names.

"Because all construction has been halted and students are on holiday, there are still many more people leaving (Beijing) than coming in," Wu said. "But we must be cautious."

Such cautiousness has meant cabbies, such as Deng Haijun, could not do business outside of Beijing from Saturday.

"On Saturday night, I was supposed to take a passenger from the Beijing airport to Tangshan city, but the security guards told him he had to instead find a hotel for the night and take a train or bus there the next morning.

"And our company wouldn't allow it either.

"It's no longer possible for a cabbie to drive someone out of the capital."

A dozen km from Zhaogongkou is Jingjintang Expressway's Dayangfang tollgate, where heavily armed Daxing district police, Beijing militia and security guards have been checking every vehicle's trunk and every driver's license. Most passengers did not need to exit the vehicles but did have to present their IDs.

In Shanghai, security checks - doubled from yesterday for the Games - went smoothly at the municipality's airports. Additional scanners went into use at Hongqiao and Pudong international airports' terminal buildings' entrances.

"The inspection process went smoothly and added no more than 10 minutes to the procedure for every passenger yesterday morning," spokesman and deputy manager of the Hongqiao airport Wang Jijie said.

The Shanghai Airport Authority said about 4,500 passengers at Hongqiao Airport underwent the special security checks from 6 am to 8:30 am.

A 42-year-old woman flying to Tianjin yesterday, who did not want to be named, said she had read a pamphlet about the special checks at her hotel before coming to the airport.

"It is understandable that China added the special checks around the Olympics, so I came here two hours earlier to be cooperative and to make sure I didn't miss my flight," she said.

Wang said rush hour came half an hour earlier than usual yesterday, because so many passengers arrived early.

Congestions formed around some entrance doors near check-in counters but were quickly cleared by airport staff.