Construction on the Neponset River bridge will be largely finished next week, and traffic is expected to return to the same level as before the project started, the Massachusetts Department of Transportation said this week.

The $34 million project will be finished by March 2013, according to DOT spokesman Michael Verseckes, five months ahead of schedule. The construction on the 42-year-old bridge started in April 2010.

The project consisted of reconstructing the concrete bridge deck and the median, replacing expansion joints, better lighting, paving and new sidewalks. The sidewalks will be 8 feet wide and compliant with the Americans with Disabilities Act, an improvement over the previously narrow sidewalks that registered at 4.4 feet wide.

Verseckes said DOT is expecting the job to be “substantially complete” on Oct. 26. Periodic lane closures will occur through March as the contractor works to complete the median divider and install railing.

The project frequently forced lane closures and caused traffic jams in Dorchester and in neighboring Quincy, since the bridge is used by 70,700 vehicles a day. The construction caused one state representative, Marty Walsh, to quip, “If we survived the Big Dig for 13 years, we can certainly survive the Neponset Bridge construction.”

The contractor for the job is J.F. White, a company based in Framingham.