Residents in the city will soon be able to rent cars for short periods under a new auto-rental model which is expected to reduce congestion and pollution in a city with more than 850,000 private cars.

The car-sharing model, one of the most popular projects displayed by Germany at the Urban Best Practices Area of the Expo 2010 Shanghai, will be promoted across the city, the Shanghai Dazhong Car Leasing Company said on Friday.

The model would be attractive to customers who only use a car occasionally, as well as to those who would sometimes like access to a vehicle of a different type from the one they use regularly.

According to the company's spokeswoman Wang Peihong, the company hopes to start operating in Shanghai some time this year after it sets up interactive platforms for online bookings.

Car-sharing, which differs from traditional car rental as it is not limited by office hours and vehicles can be rented by the minute, by the hour or by the day, originated in Zurich, Switzerland, and has been adopted in many cities in Europe.

At the recent World Expo, Bremen, a port city in Germany, gave details of its experience with car-sharing to people in Shanghai which, like many other big cities in China, is plagued by traffic jams.

Wang said the technical details for using the model in Shanghai are still under negotiation but could be released as early as February.

But in Bremen, which has a population of 548,000, only a fraction of Shanghai's population of more than 20 million, has 5,500 households registered as members of a car-sharing company which has 42 sites in the city.

People can book cars online, by phone or text message. Members do not pay for fuel, insurance and parking fees as the rental company covers these bills.

Members receive a monthly bill, which is much less than the cost of owning a car, according to information provided at the Shanghai fair.

On average a shared car can replace six private cars, the case suggested.

Many Shanghai residents approved of the idea on Friday.

They said the plan will help to remove vehicles from the streets of the city, which has already adopted policies such as charging high fees for car license plates to slow the growth rate of car ownership.

"I believe that many people will give up the idea of buying a car if they can easily use a car-sharing system," said Lu Chuan, a 24-year-old Shanghai resident.

"Hopefully it will help reduce Shanghai's vehicle density and improve air quality in the long run," he said.

Some drivers, however, were concerned about the safety of sharing a car with strangers.

"The biggest concern will be whether sharing a car with others can be safe enough," said Yang Yiqi, a 54-year-old Shanghai resident.

"What if the previous user puts something dangerous in the car which is not identified before the car is used by another driver?"

Replacing private cars with shared ones directly reduces demand for parking spaces. Even more important for congestion, the strict metering of costs provides an incentive for people to drive less.