And now they have overtaken station-based bicycles as the most popular form of shared transportation outside transit and cars in the U.S.

According to a new report released Wednesday by the National Association of City Transportation Officials, riders took 38.5 million trips on shared electric scooters in 2018, eclipsing the 36.5 million trips on shared, docked bicycles.

Riders also took trips on 3 million dockless pedal bikes, which can be picked up and dropped off anywhere, and 6.5 million dockless electric bikes in 2018, but the report notes those numbers are declining.

One reason for electric scooters' fast growth: companies are jockeying for strategic position in the so-called micromobility revolution, where consumers are embracing shared scooters and bikes for short trips and exploring alternatives to car ownership buoyed by the ubiquity of smartphones.