The improvements are the first phase of redesign plans for the roadway, nicknamed "Boulevard of Death."
One lane of Brooklyn traffic will be removed to make room for a bike path on the bridge, the DOT said.
The Plaza de Las Americas at 175th Street and Broadway will be transformed into a town square.
Transportation advocates have pushed for safety upgrades on 21st Street for the last few years.
The city is looking to install bike lanes on the bridge in the late spring, the DOT said.
Construction beneath Gansevoort Plaza is set to begin in the spring or summer, the city said.
The blueprint is part of Vision Zero, the city's plan to eliminate traffic fatalities in New York.
The extended Columbus Avenue lane will better connect it to the Ninth Avenue lane, the DOT said.
Montserrat Daubon's pieces will be installed at 155th Street and Riverside Drive.
The DOT wants to designate a slow zone in Hudson Heights and install a crosswalk on Bennett Avenue.
The DOT held a workshop in Woodside this week to get input on how to improve the roadway.
Assemblyman Joseph Lentol requested a study due to congestion in the neighborhood.
The temporary bridge will hopefully be completed in the next six to eight weeks, according to the DOT.
New crosswalks, turn restrictions and bigger medians may come to Washington and Underhill avenues.
Comptroller Scott Stringer says the issues must be repaired before the program expands next year.
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