Why Uber and Lyft Might Be Hurting Stressed Public Transit Systems

Conventional wisdom holds that the use of ridesharing services like Uber and Lyft mean that people drive less. But that doesn’t necessarily mean that less miles are being driven, and it may decrease the use of more efficient public transit.

Now, there’s new research from the University of California, Davis to validate that argument.

Researchers found that once a respondent started using a ride-hailing service, he or she is less likely to use public transit. According to the report: “Ride-hailing attracts Americans away from bus services (a 6% reduction) and light rail services (a 3% reduction).”

On the other hand, these services can complement the use of commuter rail. The survey showed a 3% net increase in commuter rail use among those who said they use shared riding services.

Related: Uber Allows Tipping

The authors concluded that ride-hailing is likely to mean that more, not less, miles are driven in the areas surveyed, which included Boston, New York, Washington D.C., and Seattle, and their immediate environs. Of those in urban areas, 29% of respondents said they use ride-hailing compared to 7% of those in the suburbs. Just over 4,000 people were surveyed, more than half of whom live in densely populated areas.

Related: Boston Uses Big Data to Ease Traffic Jams

On the face of it the findings make sense. Consider a household with one car. Until recently, family members or roommates would likely consolidate rides to make use of that asset. However, as convenient ride services became available, household members are be more likely to “split up” and take their own rides as needed. That could mean more miles travelled in aggregate, although it could mean less mileage on the family car.

Get Data Sheet, Fortune’s technology newsletter.

The report’s lead author Regina Clewlow summed it up in a statement given to SFGate: “Although we found that ride-hailing can be complementary to transit and reduce vehicle ownership for a small portion of individuals, we found that (overall) these services currently facilitate a shift away from more sustainable modes towards low occupancy vehicles in major cities.”

If that is true on a broad scale, it’s important information for cities and states to know for infrastructure planning purposes. As SFGate points out, Lyft and Uber have lots of driving data, but have been reluctant to share it with municipalities.

Subscribe to the Eye on AI newsletter to stay abreast of how AI is shaping the future of business. Sign up for free.