SHENZHEN, Jan. 6 -- The hordes of people waiting outside the Shenzhen Convention and Exhibition Center this week aren't there to see a famous artist or attend the latest job fair.

Rather, residents in the southern metropolis of Shenzhen have flooded the location to obtain certificates proving they bought their cars before 6 p.m., Dec. 29, when Shenzhen suddenly placed a cap on car purchases.

Buyers who purchase cars after that time will have to get their new car plates by lottery or auction, according to city authorities, who announced the purchase limitation 20 minutes before the policy took effect.

The restriction, aimed at easing congestion, took many by surprise and fueled panic among locals.

A resident surnamed Zhang said that after hearing about the policy, he rushed to an automobile dealer and bought the car he had always hesitated to buy. He paid an extra 20,000 yuan (3,218 U.S. dollars) for it, as sellers tried to profit from panicked buyers.

"The sudden restriction is too rude," said one resident. "As a local citizen, I only hope the coming lottery will be just and fair."

Rumors about a possible car purchase restriction had swirled prior to the official announcement, fueling a spike in license registrations in Shenzhen. According to official statistics, some 42,000 cars were registered during the first 20 days of December, a monthly expansion of 132 percent.

There are more than 3.1 million vehicles in Shenzhen, with 4 million expected in 2016, which will prolong the average evening commute from 55 minutes in 2014 to 92 minutes in 2016, according to a municipal government statement.

In 2014, the Shenzhen government repeatedly said it would not impose car restrictions, leading many locals to take the sudden move as a slap in the face. Local officials explained the urgent measure was aimed at restraining car numbers while curtailing traffic jams and environmental woes. But many question whether the restriction will work as expected.

RESTRICTION BLITZ

Shenzhen, which borders Hong Kong, is the eighth Chinese city to adopt purchase restrictions. It is not the first to resort to a "restriction blitz" to tackle rising congestion and pollution.

In March, local officials in Hangzhou in east China's Zhejiang Province launched a similar strike on car buyers, five hours before the policy went into effect. Guangzhou, Tianjin and Guiyang all chose to announce car restrictions in the evening and implement the policies at midnight the same day.

The restrictions have effectively eased traffic congestion in cities such as Shanghai, Tianjin and Hangzhou, according to local traffic reports.

Experts agreed the policy can quickly address the tricky problem of traffic congestion. Zhou Keda, a sociologist with the Guangxi regional academy of social sciences, said that with the rapid growth in private cars, a direct restriction will certainly help relieve traffic pressure.

"The restriction will also help decrease emissions," Zhou said.

But how long the restriction will work remains to be seen.

Liu Demin, a resident of Hangzhou, said when the eastern city's policy was implemented, the traffic problem eased. But now, Liu said, it seems the cars in the city are moving "like snails" again.

"When the restriction began, I could save about 10 minutes during the morning rush hours, but now it's starting to be congested again," Liu said.

According to a report published by AutoNavi, a Chinese company specializing in digital maps and navigation, Beijing remained the most congested city in China in the third quarter of 2014, with rush-hour commuters spending 2.12 times the usual length for non-rush hours, despite the city's car restrictions.

That has raised questions about the latest Shenzhen restriction. Experts say the car restriction is only a temporary measure, and a long-term mechanism is needed to eradicate problems at their root.

"The restriction can only drag on the growth of car numbers and postpone the crush of the transportation system," said Feng Yinchang, an environment expert with Nankai University. Feng said the problem does not lie in the number of cars, but in city planning.

"Car restrictions are not a cure-all for the problems caused by automobiles, such as smog, congestion and city noise," said Yang Jianhua, director at the research center of the Zhejiang Academy of Social Sciences.

Yang said these "city diseases" are shared by many countries, and the most important way to treat them is enhanced public transportation.

Cities need to focus on building complete public transport systems and improving transit service levels, Yang added.