Los Angeles’ I-405 is the nation’s busiest interstate. In an effort to loosen the iconic L.A congestion, the California Department of Transportation and the Los Angeles County Metropolitan Authority envisioned a massive widening project that would add a 10-mile high-occupancy vehicle lane to the northbound side of Interstate 405, between Interstate 10 and U.S. 101 Highway.

Selected as lead designer for what would become the I-405 Sepulveda Pass Improvements Project, HNTB would head the planning and design of the largest and most complex freeway shutdown in the history of Los Angeles. HNTB’s scope of work also included utilities, bridges, intelligent transportation systems, landscaping and other project criteria.

Coordination was critical in developing efficient staging schemes compatible with compliant traffic handling plans. In collaboration with the Los Angeles County Metropolitan Transportation Authority, Caltrans, the City of Los Angeles and Kiewit Infrastructure West, HNTB expedited the baseline design to completion in less than 18 months.

HNTB also expedited the project by using mobile LiDAR to condense surveying to just 12 hours over three nights, employing innovative technologies to accelerate bridge erection, and preventing the mother of all traffic jams, “Carmageddon,” through a massive traffic management initiative and public awareness campaign.

When completed, the project increased traffic capacity and improved public safety throughout the corridor with the addition of standardized lane widths, shoulders and ramp geometrics as well as the retrofit of existing bridges to meet current seismic code.

Location: Los Angeles, CA

Client: Los Angeles County Metropolitan Transportation Authority, California Department of Transportation