CHICAGO (CBS) — On June 28th, 2013 the Divvy Bike Program debuted in Chicago. Now it’s rolling out even more stations in the city.

“Divvy has put in an order for 40 new stations and about 400 new bikes, they expect they will arrive in the late summer,” said Mike Claffey, Chicago Department of Transportation.

“Our priority for this year, for the new stations is to increase the density in areas that don’t have a lot of stations in them and also to add some capacity at the heavily used stations that sometimes runs out of bikes.”

Claffey said the program has been extremely successful.

“It’s been a tremendous four years. We surpassed 10 million riders over the winter time and we’re heading towards 20 million,” he said.

“Divvy bikes are seen all across the city and we think they played a big role in making Chicago the number one city in America for biking. Bicycling Magazine awarded Chicago with that title last year. It’s great.”

The locations for the new bikes and stations have not yet been finalized, but Claffey said the focus is on improving the network and customer service, so some stations will be added to the existing service area, in particular in areas with a low number of stations like Chicago’s South Side.

“We are increasing our valet service this summer for special events for major concerts so people can beat the traffic when it comes to going to the beach or special events. Make sure to check the website to see if valets will be around. Events like Lollapalooza, July 4 fireworks so you can ride a Divvy.”

Divvy currently has about 5,800 bikes and 580 stations in Chicago and in the suburbs of Evanston and Oak Park.

Claffey said the transportation department wants to secure more federal clean air funds for a bigger Divvy expansion next year.

“Divvy bikers have traveled 22.9 million miles so far. There’s only great things to come,” he said.