From Downtown to the Westside: The D Line Extension That’s Redefining LA Mobility

The Westside of Los Angeles, California is more than a destination — it’s the region’s second-largest employment hub and a vital artery in the city’s economic and cultural landscape. Yet for decades, it remained disconnected from the region’s growing rail network. That’s changing with the Los Angeles County Metropolitan Transportation Authority (LA Metro)'s D Line Subway Extension Project — formerly known as the Purple Line Extension — a transformative investment in sustainable mobility. The project will connect downtown Los Angeles to the Westside.

Jacobs has been central to this effort since the beginning, leading construction management and providing design and engineering support under the design-builder. Our multidisciplinary team has tackled everything from tunnel lining and seismic joints to emergency ventilation, drainage systems and coordination across multiple jurisdictions.

Digging deep to deliver LA’s transit future

Construction on the D Line Subway Extension Project – Section 1 began in 2015 with deep tunneling through prehistoric formations and dense urban infrastructure. The project is deploying multiple tunnel boring machines (TBMs), each named by local schoolchildren to continue an LA Metro tradition that integrates community engagement into engineering. Delivered in three phases, the extension will unlock critical connections across Los Angeles County:

Section 1 of the D Line Subway Extension, delivering three new stations, is set to open in the spring of 2026:

• Wilshire/La Brea Station: Providing a key access point to the Miracle Mile and north-south transit via La Brea Avenue
• Wilshire/Fairfax Station: Serving cultural landmarks like Los Angeles County Museum of Art (LACMA) and the Academy Museum
• Wilshire/La Cienega Station: Linking to Beverly Hills, Restaurant Row and Cedars-Sinai Medical Center

All three stations are designed with sustainability in mind, featuring energy-efficient lighting, advanced ventilation systems and water-saving technologies that align with the region’s long-term environmental goals. The entire D Line Extension Project will be open in time for the 2028 Olympic and Paralympic Games in Los Angeles.

Navigating complexity both below and above ground

Jacobs’ role spans the full lifecycle of tunnel and station delivery, integrating technical precision with strategic coordination:

• Designing  tunnel linings, seismic joints and cross passage frames to withstand earthquake risks
• Engineering tunnel drainage, pumping stations, emergency ventilation and tunnel and lighting
• Conducting settlement impact assessments and structural monitoring
• Managing procurement, contract changes, quality control, scheduling and inspections across a 60-person construction management team

Working in the heart of Los Angeles requires more than engineering — it demands collaboration. Jacobs coordinated utilities with the City of Los Angeles, maintained traffic flow and navigated the unique expectations of the City of Beverly Hills, a newcomer to subway construction. We developed mitigation plans to minimize noise, vibration and air and water quality impacts, particularly near commercial developments and sensitive structures. 

The project also involved extensive documentation, with more than 10,000 submittals and hundreds of progress reports processed to maintain transparency. Safety innovations include enhanced emergency ventilation and fire protection for dense urban settings. 

Once complete, the D Line Extension will serve tens of thousands of daily riders, reducing congestion, cutting commute times and providing a high-speed connection between downtown and the Westside. 

Jacobs’ work on the D Line Subway Extension builds on a deep legacy of delivering transformative infrastructure across Los Angeles County. From expanding mobility through LA Metro’s LA River Path and A Line Extension to Pomona, to delivering the first fully automated terminal on the U.S. West Coast at the Port of Los Angeles, our teams have consistently helped shape the region’s future. We’ve supported STEAM education through the SEED School of Los Angeles County, advanced sustainability with the city’s RecycLA waste and recycling program, reimagined connectivity with the Sixth Street Viaduct Replacement and continue to provide program management on the Los Angeles Community College District’s $15.1 billion BuildLACCD Bond Program. Each project reflects Jacobs’ commitment to digging deep — into design, delivery and community impact — to help Los Angeles thrive.