Uber, the on-demand taxi service, is on course to revolutionize the way we travel in cities. It’s so popular that it has changed how we talk about other new on-demand services and it’s now valued at over $40 billion. But a team of researchers has shown that—at least in New York City—there are plenty of times when a regular old yellow taxi is cheaper than an Uber.

A group of computer scientists from the University of Cambridge and Belgium’s University of Nanmur calculated that Uber is more expensive than a yellow cab for a trip in New York City that costs less than $35, the MIT Technology Review reports.

As the research paper says, “human mobility tends to be characterised by a vast majority of short trips” and “Uber’s economical model exploits this trend of human mobility in order to maximise revenue.” The argument is that Uber’s model skews more expensive for shorter rides. In short: You should probably just wait for a cab.

OpenStreetCab

The research team figured this out by comparing a list of trip and fare data for every yellow cab ride taken in 2013 with Uber’s system, which allows anyone to query how much a fare between two points would cost. Researchers compared prices for Uber’s lowest-cost offering, Uber X, with the trip data from the NYC Taxi and Limousine Commission. Uber’s API returns a range of prices it expects the fare to be within, so the researchers averaged the range to get their comparisons.

OpenStreetCab

The team’s research also showed where in the city a ride is cheaper in a yellow cab versus an Uber. It turns out that unless you’re traveling between Manhattan and the outer boroughs, or pretty far within Manhattan, it’s usually cheaper to take a yellow cab, even outside of surge pricing.

The team has also turned its research into an iPhone app for New Yorkers, Vsevolod Salnikov, one of the researchers on the project, told Quartz, and it went live March 6. The app, OpenStreetCab, takes the team’s research and pairs it with your phone’s location and your intended destination, and tells you whether you should take an Uber or a regular cab.

It’s essentially an Uber for Ubering.