I-5 HOV Improvement Project Between SR 55 and SR 57

I-5 HOV Improvement Project Between SR 55 and SR 57

Santa Ana, California
United States

TYLin served as Prime Design Consultant for the final design phase of the Interstate 5 High-Occupancy Vehicle (HOV) Improvement Project between SR 55 and SR 57 in Santa Ana, California.

The I-5 HOV Improvement Project for the Orange County Transportation Authority (OCTA) provides a significant benefit to the traveling public by repurposing the existing width of the I-5 freeway and adding a second HOV lane in each direction between SR 55 and SR 57. Close to six lane miles of HOV lanes were added to a heavily congested portion of I-5 that will be traveled by 400,000 vehicles each day by 2035. 

TYLin's final design provides drivers with a typical HOV experience despite field conditions that required "one-of-a-kind" design details. Challenges included replacing the single-lane north- and southbound HOV lanes with two southbound HOV lanes while realigning two northbound HOV lanes into an area previously used for northbound general-purpose lanes.  

Innovative solutions included constructing a retaining wall under the abutment of an existing railroad bridge to create the space needed to accommodate northbound general-purpose lanes. Creating geometric designs to "thread" the four HOV lanes under bridges also eliminated the need to widen the southbound lanes. 

TYLin's services included project management and stakeholder coordination; roadway, structures, signing, pavement delineation, and staged construction and traffic handling design; utility coordination; and the oversight of numerous subconsultants.

TYLin also completed the complex Mandatory and Advisory Fact Sheets during the Project Approval/Environmental Document (PA/ED) phase. 

Project Highlights:

  • TYLin excelled at proactively identifying potential issues, allowing time to develop consensus on solutions and save on project costs while meeting budget and schedule requirements. 
  • Traffic patterns were evaluated to allow for expanded and extended lane closures, enabling the project to be completed close to four months early, saving tax dollars and bringing benefits to the public sooner. 
  • TYLin collaborated with OCTA and California Department of Transportation (Caltrans) staff to schedule the Main Street HOV drop-ramp bridge demolition during a single weekend freeway closure. 
  • Innovative pavement solutions were specifically designed for the site conditions, which required coordination and approvals from Caltrans Pavement Specialists.  
  • TYLin took on the unique conditions and challenges of the project and developed solutions that can be considered on future projects, redefining how projects are typically approached.  

Image credit: Brooke Duthie Photography


Construction Project of the Year, 2021
American Society of Civil Engineers (ASCE), Los Angeles, California Branch
National Honor Award, 2021
American Council of Engineering Companies (ACEC)
Outstanding Construction Project Award, 2021
American Society of Civil Engineers (ASCE), Orange County, California Branch
#9, Top 10 Roads , 2020
Roads & Bridges Magazine