All 13,000 taxis in New York City could be replaced by a fleet of 3,000 ride-sharing cars if used exclusively for carpooling, according to research published today by MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL). From a report: Instead of hailing taxis, passengers that use ride-sharing services for carpooling may lead to reduced traffic congestion, pollution, and fuel use. The CSAIL researchers used public data from NYC taxi rides published by the University of Illinois to develop the algorithm. They calculated that 3,000 four-person vehicles travelling to similar destinations could meet 98 percent of taxi demand in the city with an average wait time of 2.7 minutes. Perhaps the most important part of the system is a dynamic repositioning of vehicles based on real-time demand, which makes the system 20 percent faster.