The planned expansion of the Capital Bikeshare program is underway this month with more docking stations being added at the most popular locations where riders pick up and leave bikes in the District.

Thirty-six docks, which keep bikes securely locked between uses, were added to four stations Monday. Four other stations were expanded Friday, and a total of 18 stations will have the capacity to handle more of the red bikes when the expansion is complete.

“That’s probably been the top complaint: either full or empty stations,” said John Lisle of the District Department of Transportation.

The Bikeshare program uses vans to shuttle bikes around so inbound commuters have plenty near their homes in the morning and their offices in the evening. They also remove bikes from destination stations so there are open slots for arriving riders who want to drop off their bikes.

The expansion will continue this week, when the program begins to install docking stations in 34 new locations in the District and six new locations in Arlington.

Before the expansion, Bikeshare offered 1,100 bikes at more than 110 locations.

Alexandria decided last month that it will join the regional cycling network, with plans to install six stations with 54 bikes next year. The program might also expand to Montgomery County in 2012.