Daimler’s car2go is starting to see some real payback for its one-way carsharing business model with 40-percent growth in the first half of this year.

More than 4.5 million trips were taken in the first half of 2017 at 11 North American locations. The company also reported that customers were spending 33 percent more time on their trips than the first half of 2016. Users appreciate the convenient, affordable way to get across the city, the company said.

Growth has been helped by adding Mercedes-Benz vehicles to the fleet in January. Since then, membership has grown by nearly 100,000 new customers, the company said. The fleet had started out with the Smart Fortwo car from Daimler’s subsidiary, and this year has added the Mercedes-Benz GLA crossover and CLA sedan.

The company has taken a cautious gradual approach to doing global business. Its presence in North American started about five years ago, and has included leaving a few cities — including Miami, Minneapolis, and San Diego — that weren’t economically viable.

Competitors such as Zipcar had disagreed with the one-way carsharing model, where customers can pick up the car at a company location and drop it off near their destination. That’s opposed to returning the car to its original pickup site, similar to most airport car rental trips.

It’s taken off enough for car2go for Zipcar and Maven to offer one-way carshing services.

A university study found the car2go one-way model to be effective.

“In July 2016, we released results of our three-year study examining the impact of one-way carsharing across five North American cities. Across the cities, we found that one-way carsharing services, like car2go, were responsible for removing up to 11 other vehicles from urban streets, while also reducing carbon emissions on net,” said Dr. Susan Shaheen, co-director of the University of California Berkeley’s Transportation Sustainability Research Center.

“It’s encouraging to see that car2go’s membership not only continues to rise, but that car2go’s members are opting to choose carsharing more frequently when they travel,” Shaheen said.

SEE ALSO: Daimler’s car2go Sees Fast Growth in Chinese City of Chongqing

The company is in discussions to open shop in more cities across North America, the company said.

New York City, Toronto, and Vancouver have experienced the fastest year-over-year membership growth in the first half of this 2017. Vancouver is the largest of the 11 North American cities, with 135,000 local members. Seattle is the largest in the U.S. with more than 95,000 members, car2go reported.