Carlsbad's City Council has signed off on an agreement with regional transit agencies to advance a long-debated plan to bury downtown railroad tracks about 30 feet below street level through the Village and Barrio.
The deal, approved with the North County Transit District and the San Diego Association of Governments, advances preliminary studies and design work on the project, according to the San Diego Union-Tribune. City and transit officials have been discussing some version of this trench since at least 2009, but the current agreement marks the most concrete step yet toward a proposed project that would lower tracks along a 1.1-mile stretch.
The SANDAG board is expected to vote on the agreement later this year. The agreement outlines work to complete preliminary studies and take the trench design to 30 percent completion.
Where the Money Is Coming From So Far
Carlsbad's own share is $5.22 million, appropriated from general fund reserves back in 2023 as matching funds for the planning phase. According to The Coast News, that local contribution does not require voter approval under the city's Proposition H spending cap, because the project does not involve acquiring the tracks and the city would not own, lease, or control them — Prop H only requires a public vote for city-funded property acquisitions or municipal real estate improvements. The city's money will be paired with $20.8 million in State Transportation Improvement Program funds that SANDAG allocated this year, plus $1 million included in the fiscal 2025-26 federal Transportation, Housing and Urban Development appropriations bill, which city staff expect to offset $1 million of Carlsbad's contribution.
The preliminary studies and design phase is estimated to cost $26.1 million.
Why Officials Picked the Pricier Option
SANDAG is already working to double-track the entire coastal rail corridor through San Diego County, a stretch that has completed roughly three-quarters of its 60 miles. Double-tracking lets trains pass each other without stopping and is meant to boost both speed and service frequency — and SANDAG intends to double-track the downtown Village segment regardless of whether the tracks end up in a trench.
A street-level double-tracking alternative also exists. A 2020 Alternatives Analysis conducted by SANDAG and Carlsbad found that the 1.1-mile trench option, known as the Long Trench, scored highest among the trench alternatives.
Four Years of Disruption Downtown
If it moves to construction, the project would take about four years and cause several years of noise and traffic disruption in the Village and Barrio. Trains would be diverted onto a temporary parallel shoofly track for much of that span, and the North County Transit District has estimated crews would need to excavate between 400,000 and 600,000 cubic yards of earth over 8 to 12 months.
The trench itself would run from the Buena Vista Lagoon near the Oceanside border south through the Village and Barrio to about Tamarack Avenue. North County Pipeline reports the design also includes an elevated rail bridge over the lagoon engineered to withstand high tides and sea-level rise, a climate consideration that echoes concerns Carlsbad has raised elsewhere along its coastline, including its recent emergency declaration over the crumbling Highway 101 coastline.
A Growing Corridor
Regional planners expect train traffic through Carlsbad to roughly double to about 100 trains per day by 2035, a forecast driving the broader push to finish double-tracking the corridor.
The Carlsbad segment sits along a 60-mile coastal rail line in San Diego County.
The downtown trench proposal is separate from other double-tracking work already underway in Carlsbad. SANDAG and NCTD broke ground in late 2024 on a $166 million Batiquitos Lagoon project to add nearly a mile of double track and replace an aging trestle bridge in southern Carlsbad, part of the same regional effort to clear the last single-track bottlenecks on the coastal line.
