It’s an elusive missing link in Los Angeles’ freeway system: A 6.2-mile dotted line on the map that transportation planners have for decades hoped would connect the Foothill Freeway in Pasadena with the Long Beach Freeway in Alhambra. But that dotted line runs through a historic neighborhood of California Craftsman homes and tree-lined streets in South Pasadena. For nearly 50 years, residents there have fought the freeway. Just as tenaciously, residents of nearby traffic-weary cities, particularly Alhambra, have battled to have it built. Now, some officials believe the solution to the standoff might lie beneath their feet. Earlier this month, they persuaded Congress to approve $2.4 million to study the possibility of extending the freeway through a five-mile, $2-billion tunnel that would run under South Pasadena and part of Pasadena.
Article here. A recent Reason study examines how we can get California moving again by using public-private partnerships. The authors point to another spot in LA where tunneling makes sense:
[A] toll tunnel linking Palmdale with Glendale would dramatically shorten the commute time to Pasadena and downtown LA, while also paving the way for Palmdale Airport to attract major airline service. With a cost of $3 billion, toll revenues would cover all of the costs if the project was completed in two phases, or 83 percent of the costs if built all at once.