The city’s public bike share system Hubway will undergo the largest single expansion since its launch in Boston in 2011, according to a statement from Boston Mayor Martin J. Walsh.

Over the next two years, more than 70 new bike stations will be added to the 127 stations currently in existence in Boston, representing a more than 55 percent increase in bike stations located across the city.

The expansion comes after the Boston Transportation Department (BTD) negotiated a new long-term contract with Motivate, International to operate the publicly owned Hubway system.

“To further improve the system, the majority of Hubway stations will now operate in the city of Boston year-round, continuing service to residents and other members throughout the winter months,” Walsh said in a statement.

The expansion new service improvements will be introduced in the coming months. Additional service improvements will include more valet services where users are guaranteed bikes and docks at high-demand locations, and techniques to make sure bikes and empty docks are more available at every station.

The Hubway network will grow in Cambridge, Somerville and Brookline as well. Together with Boston, the municipalities also approved long-term contracts with Motivate.

Planning for Boston’s bike share station expansion will begin in the early summer, with public meetings to be held in neighborhoods across the city. The BTD expects to reach new neighborhoods with bike share, including Dorchester, Roslindale and Mattapan. Dozens of new stations and docks will also be added in Boston’s existing service area to better meet current demand.