RIVERSIDE (CBSLA.com) — The 91 Freeway in Riverside will be shut down for part of this week in what some officials are calling “Carmageddon” in the Inland Empire.

The overpass closure at the 14^th Street Bridge began Sunday at 11 p.m. and will continue nightly from 11 p.m. through 6 a.m., ending Wednesday morning.

All lanes, except one in each direction, will be closed as the northern half of the bridge is demolished.

Approximately 35,000 vehicles use the bridge during the work week to access downtown Riverside, according to Caltrans.

The closure is part of a more than $230 million freeway widening project that will add a carpool lane between the 91, 60 and 215 freeway interchange at Adams Street.

Caltrans said lane reductions will continue on the 14th Street Bridge while the entire overpass is rebuilt, reducing the capacity to about 15,000 vehicles per day.

Drivers can use the existing 14th Street ramps as detours.

It is scheduled to be completed in early 2013.

For updates, visit SR-91 HOV Project.