Stockton Diamond Makes Grade

Train crossing the diamond junction in Stockton

On first view, it’s a little disconcerting. Two sets of double tracked railroad tracks cross each other at right-angles.  Its a diamond junction, named for the shape it creates when viewed from a corner.  But it feels more like a busy four-lane road intersection, except with 100-car freight trains rolling though.Welcome to the Stockton Diamond–the busiest and most congested rail junction on the west coast.  Trains pass through heading up and down the west coast and from the Port of Oakland to all points east. It’s a major pass-through for much of the San Joaquin Valley’s rich agricultural harvest.   It’s also an important junction for passenger rail; both the Altamont Commuter Express and the Amtrak San Joaquins pass through on the way to the Bay Area.

Just to the southeast of downtown Stockton, the junction also serves many local uses. Just five blocks to East is a major yard for the BNSF Railroad. Eight blocks South is another yard for the UP Railroad.  Ten blocks West is the rail entry for the Port of Stockton.  And eleven blocks North is the terminus of the Altamont Commuter Express.

Currently, freight and passenger service is limited through this corridor due to the existing congestion caused by the at-grade crossing.  Untangling the junction supports plans to expand both the ACE commuter rail service and San Joaquin Amtrak service between the San Joaquin Valley, Sacramento, and the Bay Area.

Eliminating a Bottleneck

The solution is to construct a grade crossing (or “flyover bridge”) so that the North-South tracks will pass over the east west tracks.  Grade separated double tracking will also improve the efficiency of the ACE rail.  The project also includes bike, pedestrian, and roadway improvements and safety enhancements at several at-grade local road crossings in the City of Stockton.

Separating the grade will provide for an uninterrupted flow of rail through the crossing, which will improve freight movements and lead to lower costs for freight shipping, reduced delays, and a decrease in fuel consumption for idling locomotives. This increase in throughput translates to cost savings for Port customers and the freight railroads. In addition, the project would allow for more freight and passenger trains to pass through the Stockton Diamond at faster speeds.

Another project benefit includes improved air quality from the reduction of idling locomotives (and cars waiting for the stalled trains.

Left: Aeriel view of Stockton Diamond; Right: Preliminary Flyover Grade Separation design

Strong Partnerships BUILDs Success

In September, the US Department of Transportation awarded a $20 million Better Utilizing Investments to Leverage Development (BUILD) grant. It is one of just two awards to the State of California during the 2020 cycle and the only rail project in the United States to be selected.

And in December, the California Transportation Commission (CTC) awarded another $100 million in funds from the Trade Corridor Enhancement Program (TCEP).  It was, one of only three rail projects awarded by the CTC.

Additional applications will be made to the INFRA program and the state’s Interregional Transportation Improvement Program (part of the STIP).

This success derives from the strong partnerships that have developed between the California Department of Transportation (Caltrans) and the San Joaquin Regional Rail Commission (Rail Commission).  Working together (and with strong support from the railroads), they have secured half of the funding needed to deliver the project.

“This critical project will improve both passenger and freight rail while pushing economic growth in the San Joaquin Valley,” said Caltrans Director Toks Omishakin. “The project will help reduce delays, improve air quality and expand access to the Port of Stockton.”

Role of San Joaquin Council of Governments

The Rail Commission itself is an integrated partner of the San Joaquin Council of Governments (SJCOG).  All six full-voting members of the San Joaquin Regional Rail Commission (SJRRC) are appointed by the SJCOG board.  Ex-officio members represent Caltrans District 10, the San Joaquin Regional Transit District (SJRTD), SJCOG, and the Stanislaus Council of Governments.

The Commission was formed to by the County of Stockton and SJCOG to address the emerging need to address the county’s emerging commuter rail needs of San Joaquin County residents.  Together, the County and SJCOG formed and funded the Rail Commission – including an ongoing contribution of the 30 percent of the funds raised through San Joaquin County’s “self help” transportation measure.  It currently owns, operates, and is the policy board for the Altamont Commuter Express service.

Improvements for Passenger Rail

The Rail Commission is currently in the planning and environmental phase of its nearly $1 billion “Valley Rail” service expansion program for both ACE and Amtrak San Joaquins. The Valley Rail Program will implement two new daily round trips for the Amtrak San Joaquins service and extend ACE service between Sacramento and Merced. It also supports converting the San Joaquins train and thruway bus network to renewable diesel fuel and is a key component to improving air quality in the region.

A key element of this plan was to obtain greater route certainty that a fly over bridge at the Stockton Grade Crossing would provide.


The Stockton Diamond Grade Separation project will make goods and passenger movement more efficient along the West Coast, and the San Joaquin Valley a more attractive place to do business according to Kevin Sheridan, the Rail Commission’s director of capital projects. It will also have a positive effect on Stockton’s air quality by eliminating the need for locomotives to idle as they wait for crossing trains.

“This project is a critical step in unlocking freight and passenger rail mobility in Northern California,” Sheridan said.

More Information

Four Benefits of the Project
  • Sustainability. Improve air quality through reduction of greenhouse gas caused by trains and vehicles who sit idling due to congestion and delays at the existing Stockton Diamond.
  • Enhance Safety. Improve access and mobility for City of Stockton residents through crossing closures, as well as bike, pedestrian, and roadway improvements at multiple roadway/railway grade crossings.
  • Economic Vitality. Reduced delays and fuel consumption; Increased goods movement throughput and train velocity resulting in cost savings for transportation.
  • Inspire Connections. Support faster, more reliable passenger rail travel options and expansion of service linking travelers to friends and family gatherings, employment and key destinations throughout Northern California.


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