California Bridge Law and the 40-Foot Kingpin Rule

California runs the federal axle limits and bridge formula, then adds the strictest kingpin-to-rear-axle (KPRA) rule in the country: 40 feet to the rearmost axle on a 53-foot trailer. That geometry cap — not the weight — is what catches most out-of-state drivers.

By Avery Schwartz · Former CDL-A driver, 3 years OTR · Updated 2026-09-15

The numbers at a glance

Limit	CA	Where it comes from
Gross weight	80,000 lb	CVC 35551 table; federal cap on the Interstate
Single axle	20,000 lb	CVC 35550
Tandem axle	34,000 lb	CVC 35551; two tandems at 34,000 each need 36 ft first-to-last axle
KPRA / wheelbase	40 ft to rearmost axle (2+ axles); 38 ft single axle	CVC 35400; applies to semitrailers over 48 ft up to 53 ft
Bridge formula applies?	Yes — statewide	CVC 35551 table mirrors the federal formula

Legal limits change and enforcement varies by road. Confirm anything you're betting a ticket on with Caltrans / CHP.

How California applies the bridge law

On weight, California is not unusual. The state's own axle-spacing table in Vehicle Code 35551 produces the same numbers as the federal bridge formula, the tandem limit is 34,000 lb, and 80,000 lb is the ceiling for a five-axle tractor-trailer. The 36-foot rule is written into the same section: two tandems can each carry 34,000 only when the distance from the first drive axle to the last trailer axle is at least 36 feet.

The rule that makes California its own planet is length geometry. Under CVC 35400, a semitrailer longer than 48 feet (up to 53) is legal on the STAA network only if the distance from the kingpin to the rearmost trailer axle is 40 feet or less — 38 feet if the trailer has a single axle. Note the measuring point: California measures to the rearmost axle, not the center of the tandem, which makes it roughly two feet tighter than the 41-foot-to-center rule most eastern states use. On a typical 53-foot van, that means your tandems cannot sit at the back of the slider rail; most fleets mark a "California hole" on the trailer and expect you to be at or ahead of it.

Caltrans publishes which routes are on the STAA network and which are limited to the state's shorter legal-length trucks. Off the STAA network, the rules get stricter still, so if your route leaves the Interstate, check the Caltrans truck-route map before you commit.

How to slide your tandems for California

California's 40-foot KPRA cap is the constraint you plan around. If the trailer's California hole is, say, hole 8 from the front, you can slide forward from there freely but never back past it. Forward moves weight onto the drives — so a load that scales with only a few hundred pounds of drive margin in Arizona may have no legal California configuration at all. Run the numbers before you leave the shipper, not at the Needles scale.

Worked example. You scale at the first CAT after the shipper: steer 11,800, drives 35,300, trailer tandems 31,900, gross 79,000. Gross is legal; the drives are 1,300 over. Sliding the tandems forward (toward the cab) moves weight from the drives to the trailer axles. On a trailer with 4-inch hole spacing, a hole is worth roughly 250 lb, so 1,300 lb needs six holes: drives about 33,800, tandems about 33,400. Both groups are under 34,000 with a few hundred pounds of margin, and the gross hasn't changed. Now check the geometry for California using the row in the table above — and if you'll cross into a stricter state, set for that one instead. The Tandem Slide Calculator does the hole math for your trailer's actual rail spacing and tells you which direction to move.

Common tickets in California

Based on the statutes above and what drivers commonly report; citation practice varies by officer and county, so treat this as a watch list, not a fine schedule.

KPRA over 40 feet on a 53-foot trailer (CVC 35400) — commonly reported at the Banning, Needles, and Cordelia inspection facilities. Legal weight does not excuse illegal geometry.
Axle group over the 35551 table after sliding forward for the kingpin rule and pushing the drives past 34,000.
Off-network operation — running a 53-foot trailer on a route that is not STAA-designated. Fines and requirements vary by court; verify with CHP.

California bridge law FAQ

Is California kingpin measured to the rear axle or the center of the tandem?

To the rearmost axle for trailers with two or more axles (40 ft max), and to the single axle for one-axle trailers (38 ft max). That is why a trailer that is fine at 41 ft to center in Florida can be over in California.

Does California use the federal bridge formula?

Yes in practice. CVC 35551 contains a table of maximum weights by axle spacing that produces the same results as the federal formula, plus the 36-foot two-tandem rule and the 80,000 lb ceiling.

Can I run tandems all the way back in California if I'm under 80,000?

Not on a 53-foot trailer. Gross weight doesn't matter for the KPRA rule; the kingpin-to-rear-axle distance must be 40 feet or less regardless of load.

What if the load only scales legal with the tandems past the California hole?

Then it isn't a legal California load as loaded. Options are reworking the load at the shipper, reducing fuel weight, or getting a permit. Sliding cannot fix it.

Sources

This page is a driver's summary, not legal advice. Statutes are quoted or paraphrased from the sources listed; where we couldn't verify a figure from an official source we've said so.