The state Department of Transportation said it expects major congestion and delays as summer vacations come to an end, school resumes and many people head back to work.
Construction work began last month on the much-anticipated project to replace the Route 495 Bridge.
One lane of travel was closed in each direction on Route 495 to begin long term construction on the bridge between Route 3/NJ Turnpike and Kennedy Boulevard and the ramps from Route 495 westbound to Paterson Plank Road and the ramp to Route 1&9 south.
The exclusive bus lanes will still operate in the morning.
The closures are expected to snarl traffic for the next two and a half years.
Commuters are being advised to seek alternate routes in and out of the city.
DETAILS: What you need to know about the Route 495 project
The bridge itself is nearly 80 years old, and more than 150,000 motorists use it every day.
It is now considered structurally deficient and functionally obsolete. Officials say the deck replacement work now getting underway is long overdue.
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