Away from the through routes, but often connecting to them at one end, are what were once known as Branches, but now are more commonly referred to by terms such as "Industrial Lead". Many of these were built to service long-gone industries, such as citrus packing sheds, and in other cases still serve oil refineries.
The Santa Ana Industrial Lead, one the Santa Ana Branch, branches off one of the Lines to the Harbor—the Los Nietos Subdivision—at the south end of the Studebaker Wye, South Studebaker (MP 497.4), where the maximum speed is 10 mph, and heads east-southeast, single track, unsignaled, through an industrial part of, first, Los Angeles County, and then Orange County, continuing later into areas that once were orange groves and now are completely built-up as residential areas or light industry.
The maximum speed rises to 20 mph, past an angled bridge over Imperial Highway, grade crossing with Pioneer Boulevard, San Antonio Drive, and Funston Avenue, Norwalk (MP 499.1), where Front Street is alongside to the north, grade crossings at Rosecrans Avenue, Bloomfield Avenue, Shoemaker Avenue and Carmenita Avenue, industrial spurs on the west side trailing in, a small yard on the north side at Carmenita (MP 501.2), and an industrial spur on the south side heading away, and then returns to 10 mph, past grade crossings at Alondra Boulevard, Marquardt Avenue, Valley View Avenue, Artesia Boulevard, and Knott Avenue.
Entering Orange County, and passing from La Mirada into Buena Park, the line now comes directly along the south side of Interstate 5 (the Santa Ana freeway). When the highway as just two lanes in each direction, the railroad was clearly visible alongside to the south, but with the expansion of I-5 to many more lanes, the railroad is sometimes too close to the highway for the intersection streets to cross at grade. Those that do have caused the railroad to be raised up to match their current elevation. The line passes more industrial spurs on the south side, heading away, an industrial spur on the south side, trailing in, grade crossings at Western Avenue, Beach Boulevard and Stanton Avenue, and Buena Park (MP 504.4).
Orangethorpe Avenue and several ramps of the I-5, SR 91 interchange pass overhead, Magnolia Avenue bridges overhead, as does La Palma Avenue, and Brookhurst Street, Euclid Street crosses at grade, a freeway ramp bridges overhead, the intersection of Lincoln Avenue and Loara St. bridges overhead, and there is a grade crossing with Mable Street on the wye at West Anaheim (MP 509.0), where the Stanton Industrial Lead departs to the south, the line crosses Broadway and Manchester Avenue at grade, turning just north of due east, where the branch once turned south-southeast, and bridging over I-5 on a curved bridge as it does so.
Entering the middle of Santa Ana Street, the line crosses West Street, Harbor Boulevard and Anaheim Boulevard at grade, to the former wye at Anaheim, where there was once a connection with the erstwhile UP Anaheim Branch, and the line turns just east of due south, crossing out of Santa Ana Street, crossing Philadelphia Street at grade, and running down the middle of Olive Street, crossing Water Street, South Street, Vermont Avenue, Ball Street, and Cerritos Avenue, to the wye at South Anaheim (MP 512.3), where the maximum speed is 5 mph, the branch once continued south-southeast, the Tustin Industrial lead heads east, and in the southwest quadrant of CP College, connects into the Metrolink Orange Sub.
Just south of Metrolink's Santa Ana, the Santa Ana Industrial Lead restarts, where the branch was once immediately adjacent to the west, at Santa Ana (MP 517.2), splitting off from the west side of the Metrolink line and heading due south, maximum speed 5 mph on the connection and 10 mph thereafter, past a grade crossing at Chestnut Avenue, a grade crossing at McFadden Avenue, a grade crossing at Edinger Avenue, a grade crossing at St. Gertrude Place, and a grade crossing at Warner Avenue, then past Dyer (MP 519.4), a junction where the branch once continued south and today's remnant turns west, past grade crossings of Evergreen Street, Hallady Street, and Orange Avenue.
At South Santa Ana, where an erstwhile Pacific Electric line once joined from the northeast, today's line takes up the route of that former PE line, turning south-southwest, past grade crossings at Main Street, and Dyer Road, and west, past Bristol, and grade crossings at Bristol Street, a business park, Bear Street, Raitt Street, Greenville, Fairview Street, and Susan Street, to the former junction at Costa Mesa (Greenville, MP 523.0), where an erstwhile PE line to Huntington beach once continued west, and the remnant of the line, now out of service, turns south, past still extant grade crossings at MacArthuer Boulevard and Lake Center Drive, and then vanishes before reaching the former End of Track (MP 523.9)