The northbound Santa Ana Freeway onramp at South Street closed permanently this week to allow for construction of a new freeway access.
A new northbound freeway onramp at West Street will be built. Southbound drivers also will benefit from a new carpool offramp and new onramps and offramps at West and Manchester Avenue.
Drivers who normally use the south onramp to get on the northbound freeway are advised to use the Lincoln Avenue ramp.
The improvements are part of the $1.1-billion Santa Ana Freeway project through Orange, Anaheim, Buena Park and Fullerton.
Major features include new carpool lanes and ramp upgrades.