BOSTON - One promise of ride-hailing companies like Uber and Lyft was a drop in the number of cars clogging city streets.

  

But recent studies in cities from Boston to New York to San Francisco suggest the opposite: that the companies are pulling riders off buses, subways and bicycles and putting them in cars instead.

  

A new wrinkle is a service by Uber called Express Pool that links riders in the same area who want to travel to similar destinations. Critics see it as directly competing with mass transit.

  

The companies have pushed back against the reports. They say ride-hailing is making it possible to reduce the number of personally owned cars on the roads.

  

A study of traffic woes in London instead placed blame for congestion on construction and delivery trucks.