What Happened to 405 Freeway Closure (Carmageddon)?

The phenomenon dubbed "Carmageddon" first captured public attention in Los Angeles in 2011, referring to a planned 53-hour closure of a 10-mile segment of the I-405 freeway through the Sepulveda Pass. This unprecedented shutdown, from July 15-17, 2011, was necessary for the demolition of the southern half of the Mulholland Drive Bridge as part of the larger I-405 Sepulveda Pass Improvements Project. Public officials, including County Supervisor Zev Yaroslavsky who coined the term, issued dire warnings of apocalyptic traffic jams, prompting an extensive $5 million public awareness campaign urging residents to stay home, use public transport, or seek alternate routes.

Contrary to the widespread fears, the first Carmageddon resulted in remarkably light traffic, with volumes on the affected freeway segment decreasing by 61% northbound and 73% southbound compared to typical summer weekends. This unexpected outcome, often dubbed "Karmageddon," saw Angelenos embracing local activities, biking, and utilizing public transit, leading to a temporary reduction in air pollution and a newfound appreciation for local neighborhoods. A second, similar closure occurred in September 2012 to demolish the northern half of the Mulholland Bridge, also proceeding with minimal traffic disruption.

The underlying I-405 Sepulveda Pass Improvements Project, a $1.1 billion endeavor, aimed to add a 10-mile High-Occupancy Vehicle (HOV) lane and improve supporting infrastructure. While initially expected to be substantially complete by May 2013, it was largely finished by August 2014. However, long-term analyses have cast doubt on the project's effectiveness in alleviating congestion. A 2019 study, for instance, indicated that rush-hour speeds on the southbound 405 through the Sepulveda Pass had actually decreased since the project's completion, and a 2025 report highlighted that traffic was worse than before construction began, failing to deliver promised mobility benefits.

As of June 2026, the I-405 corridor is once again a site of significant construction. Caltrans initiated a new $143.7 million I-405 Pavement Rehabilitation Project in Summer 2025, covering a 10.2-mile stretch between Van Nuys and Westwood. This project involves replacing sections of two lanes in each direction, repairing other lanes, and upgrading various safety features. The rehabilitation work has led to a series of extended weekend lane reductions and overnight closures, occurring roughly twice a month and expected to continue into mid-2026 and through Winter 2027/Early Spring 2028. These ongoing closures have again caused substantial traffic impacts, with some commuters referring to them as a new "Carmageddon."

Looking ahead, Metro and Caltrans are also planning the I-405 Sepulveda Pass ExpressLanes Project, which aims to convert existing HOV lanes into dynamically priced High-Occupancy Toll (HOT) lanes between the I-10 and US-101 freeways. The Final Environmental Impact Report/Statement (EIR/EIS) for this project is expected in 2026, with construction potentially commencing as early as 2029. This indicates that the I-405, a critical artery for Los Angeles, will continue to be a focus of major infrastructure projects and associated traffic disruptions for the foreseeable future. On June 5, 2026, an unrelated police chase and shooting caused a full closure of northbound 405 lanes in Westchester, further highlighting the freeway's susceptibility to sudden, impactful closures.