A recent inspection of the Washington Street Bridge, which carries the roadway over the DuPage River between Chicago and Aurora Avenues, showed major deterioration, the city said earlier this week.
In response, the city is closing a lane of traffic in each direction until the 40-year-old bridge can be replaced.
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The closures start Thursday.
The bridge replacement project is expected to begin next spring. Preparations to replace the bridge have been ongoing for several years, the city said.
The inside eastbound lane on Aurora Avenue will also be converted into a left-turn-only lane between Webster and Main streets and closed between Main and Washington streets, and the outside southbound lane on Washington Street will be converted into a right-turn-only lane between Jackson and Chicago avenues.
City officials are asking drivers to use alternate routes if possible.