Here’s a good example of how the sharing economy can reduce traffic congestion, pollution, and carbon emissions. According to a new MIT study, 3,000 ride-sharing cars—if used exclusively for carpooling—could replace all 13,000 taxis in New York City. The researchers calculated that 3,000 four-person vehicles traveling to similar destinations could meet 98 percent of taxi demand in the city with an average wait time of 2.7 minutes.