Traveling on Comm Ave is about to get safer, for bicyclists, pedestrians, and drivers. State transportation authorities have approved a $20.4 million reconstruction of Commonwealth Avenue between Brookline and Boston, from the BU Bridge to Packard’s Corner, an upgrade that will include long-awaited cycle tracks between parked cars and sidewalks.

Michael Donovan, the University’s vice president for real estate and facility services, says the project, which will begin early next year, should be completed in three years.

After years of debate about how to make Comm Ave safer for cyclists and pedestrians, a joint BU-city working group in 2013 recommended more warning signs, better bike lane markings, and highway reflectors. The city unveiled the cycle track plan in March 2015.

Comm Ave is one of the most heavily trafficked thoroughfares in Boston; about 35,000 vehicles, 30,000 pedestrians, and 27,000 Green Line T riders use it daily, according to the Massachusetts Department of Transportation (MassDOT). The commonwealth estimates that about 3,000 cyclists a day used the road in 2014.

MassDOT highway administrator Tom Tinlin says the stretch of roadway has had an “inordinate” number of bicycle crashes. More than 75 percent of the 121 bike accidents that the BU Police Department responded to from 2010 to 2015 occurred on Comm Ave.

The overhaul will move and widen bike lanes, now located between parked cars and traffic lanes, on the stretch of pavement between Packard’s Corner and the BU Bridge. The new bike lanes, which will range in width from five to six and a half feet and line both sides of Comm Ave, will be separated from traffic by a row of parked cars and by three-foot-wide raised buffers between the parking lane and the cyclists, a design similar to one used on some Manhattan streets. The outbound side of the street, which currently has three lanes, will lose a driving lane, bringing it down to two lanes. The inbound side of the street, which currently has only two lanes, will not lose a lane.

David Anderson, MassDOT’s deputy chief for design, says the cycle track will eliminate the hazard of a car door swinging into a bicyclist’s path, and new traffic islands will mean pedestrians have a shorter distance to cross.

Another major upgrade to the area will take place in the summers of 2017 and 2018, with an $81.8 million replacement of the Commonwealth Avenue deck over the Mass Turnpike.