The protected bikeway will separate a bike lane on Broadway heading east and on Third Street heading west between Golden Avenue and Alamitos Avenue, spanning about 2 miles in each direction.
The website BikeLongBeach.org shows what the project will look like when it's finished.
Construction is expected to be completed by March.
The bikeway will have a painted median and a curb next to street parking to separate bikes and cars. The city wants to make the downtown area more bicycle-friendly and safe.
Local transportation funds are paying for the new bike lanes, which will be modeled after a similar design in New York City. The money is not coming out of the general fund.
The project will reduce vehicle lanes on Third Street and Broadway from three lanes down to two.
Special bike signals have already been installed but not activated at intersections as a safety feature.
The bike-lane construction will impact parking in Long Beach, as a traffic lane is being taken away. There will be 13 percent fewer parking spaces for construction streets. During construction, residents will be able to park in city lots for free.