A computer model developed by researchers at MIT shows that just 3,000 Uber and Lyft vehicles, when carpooled, could replace New York City’s entire 14,000-strong taxi fleet. It’s a finding that highlights the potential for ridesharing apps to revolutionize transportation in big cities.

To make this efficiency a reality, however, most passengers would have to use the carpool feature on their Uber or Lyft apps, requiring them to share their ride with others and make multiple stops along the way.

Ridesharing, love it or hate it, is transforming the way we get around—and not just because it’s cheap. These services, as the new study attests, can significantly reduce the negative impact of traffic. Over the course of a single year, congestion costs Americans roughly $121 billion in lost revenue, 5.5 billion hours of time spent sitting in traffic jams, and an additional 2.9 billion gallons of fuel burned. Traffic also contributes to higher accident rates, pollution, and greenhouse gas emissions.

It’s unlikely that every single Uber, Lyft, or VIA user is going to suddenly start choosing to carpool to reduce traffic and help the environment. But if algorithms like this are integrated into these apps, and if passengers buy into the system, carpooling could start to become a more attractive option.