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Taxi-sharing services could reduce the number of cars on the road by 75%, a study has suggested.

The Massachusetts Institute of Technology (MIT) study found that a fleet of 3,000 four-passenger taxis could do the same job as the current fleet of 13,000 yellow cabs in New York City.

But it would mean that people would have to travel with strangers.

The study was based on data from 3 million taxi rides.

Most experts looking at our urban future agree that there is a real need to do something about congestion.

Studies suggest that globally people waste 7 billion hours each year sitting in traffic and the effects on the environment are also severe - with cars in traffic burning an extra 3 billion gallons of fuel.

"Instead of transporting people one at a time, drivers could transport two to four people at once, resulting in fewer trips, in less time, to make the same amount of money," writes Prof Daniela Rus from MIT's Computer Science and Artificial Intelligence Lab.

The team developed an algorithm that could reroute cars based on real-time requests.

"A system like this could allow drivers to work shorter shifts, while also creating less traffic, cleaner air and shorter, less stressful commutes," said Prof Rus.

Such a system would be particularly suited to autonomous cars, she added.

Ride-sharing schemes are growing in popularity, with well-established firms such as Uber and Lyft leading the way. According to Lyft, 50% of rides taken in San Francisco in 2015 were shared.

There are also lots of new options on the scene, such as DriveNow, a car-sharing service operated by BMW, which has around 200,000 customers in Berlin, or a pilot from Toyota that was recently launched in Dublin.

Not all succeed - Car2Go recently announced that it was discontinuing services in Stockholm, a city keen to promote alternative modes of transport and cut pollution, due to lack of demand.