As the first Measure M project, the SR-57 sets an ongoing Measure M precedent — finishing ahead of schedule and under budget with completion in 1992. The project added carpool lanes and merging lanes from the I-5/SR-22/SR-57 interchange to Lambert Road.

In early 2000, additional improvements were completed at the Riverside Freeway (SR-91) interchange that added a direct carpool connector from eastbound SR-91 to northbound SR-57 and the reverse movement. The lanes were also later extended into Los Angeles County.

Feasibility Study to Examine Adding an Additional Lane
A feasibility study was later conducted by OCTA to examine adding an additional lane in each direction between the Los Angeles County line and the I-5/SR-22/SR-57 interchange. This study concluded that because of extensive right-of-way impacts and expanded traffic at the interchange, consideration should be deferred until the SR-57 is extended southward toward the San Diego Freeway (I-405).

Two Segments Identified for Expansion
The study also recommended the corridor would benefit from operational improvements such as additional merging lanes, and a project study report was completed in 2005 for these projects.

The Orangethorpe to Lambert segment was the first section to be approved with the completion of the environmental phase in December 2007. The project is currently in the design phase and construction is scheduled to begin in summer 2010, depending on state funding availability.

The Katella to Lincoln segment entered the design phase in 2009 and construction is scheduled to begin in summer 2011, depending on state funding availability.