Despite being heralded as services that will reduce congestion on our streets, ride-hailing companies like Uber and Lyft actually are making traffic problems worse, a new study from Boston’s Northeastern University has revealed.

The study showed that in many cities rather than encouraging commuters to leave their own personal vehicles for shared rides, the apps are instead siphoning ridership from higher-capacity transportation options such as buses and subways. The report also found that riders do not use the apps to connect to existing public transportation lines, as Uber founder Travis Kalanick has suggested, but primarily to travel directly to their final destinations.

A survey cited in the report of more than 4,000 adults in seven of the United States’ largest metro areas revealed that between 49 and 61 percent of ride-hailing trips would have been made by other options, or not made at all, if the service didn’t exist. To make matters worse, a case study conducted in San Francisco last summer found that the increased congestion occurred in areas of the city that already suffered from the worst traffic issues.

With the launch of Uber’s Express Pool service this week – which connects riders to efficient stops along their route, instead of an exact location (an idea lifted from other express ridesharing apps such as Via) – experts fear that the problem may only be exasperated going forward.

Read the full story from the Associated Press, here.