California’s Oversize Rule: What Counts as Oversize and How to Move It Legally

In California, a vehicle or load is “oversize” if it exceeds 8 feet 6 inches in width, 14 feet in height, certain length limits (often 65 feet overall off the federal STAA network), or the standard weight limits; moving such loads generally requires a Caltrans transportation permit and compliance with route, time-of-day, escort, and marking conditions. This article explains the thresholds, permits, operating restrictions, and practical requirements that apply when transporting oversize and overweight loads on California state highways in 2025.

What “oversize” means under California law

California sets baseline size limits in the California Vehicle Code (CVC) and applies them on state highways. If your vehicle or load exceeds these, it is treated as oversize and permit-controlled by Caltrans (and often by local agencies on city or county roads).

• Width: 8 feet 6 inches (102 inches) maximum on most state routes; some local roads may be posted at 8 feet (96 inches).
• Height: 14 feet maximum. Operators are responsible for ensuring safe clearance; heights above 14 feet require a permit.
• Length: Limits vary by configuration and route:
  

  • Single vehicle: generally 40 feet (some buses up to 45 feet on approved routes).
  • Truck-tractor/semitrailer: California allows 53-foot semitrailers on the federally designated STAA network and terminal access routes; off that network, overall length is often limited to 65 feet without a permit.
  • Kingpin-to-rear-axle (KPRA) limit: commonly 40 feet in California for 53-foot trailers except where STAA rules provide otherwise.

• Overhang: Rear overhang beyond 4 feet must be flagged (and lit at night); unusual overhangs can trigger permit and escort requirements.

Any dimension that exceeds these baseline limits makes the load oversize. Separate but related limits apply to axle and gross weights; exceeding those triggers “overweight” permitting in addition to, or instead of, oversize rules.

When you need a Caltrans transportation permit

You need a Caltrans oversize/overweight (OS/OW) transportation permit to operate on state highways whenever you exceed the legal size or weight limits. Local streets typically require a separate city or county permit.

• Oversize permit: Required for width over 8’6″, height over 14′, or length beyond legal limits for your configuration/route.
• Overweight permit: Required if you exceed 80,000 pounds gross, 20,000 pounds on a single axle, or 34,000 pounds on a tandem (federal bridge limits apply on Interstate routes; California legal and bridge formula rules apply on others).
• Permit types: Single-trip permits for specific moves and dates; annual/repetitive permits for qualifying loads within set envelopes and routes.
• Routes: Caltrans may specify the exact route, districts, and any detours/closures. Local agencies control their own roads and may impose additional conditions.

Permits spell out your allowed dimensions, routes, dates/times, required escorts, signs, flags, lighting, and any special conditions. You must carry and follow the permit at all times during the move.

Operating hours, holidays, and urban curfews

Oversize moves in California are often limited to lower-traffic periods for safety and congestion management. Permit conditions vary by district, route, and size.

• Daylight travel: Many oversize loads are restricted to daylight hours (typically 30 minutes before sunrise to 30 minutes after sunset), especially on two-lane highways.
• Night travel: May be permitted on some multi-lane freeways for moderate oversize loads when specifically authorized on the permit and properly lighted/marked.
• Holidays and peak periods: Travel is commonly prohibited or restricted on major state holidays and on certain holiday eves. Urban rush-hour curfews are often enforced in metro areas such as Los Angeles and the San Francisco Bay Area.
• Weather and wind: Permits may prohibit travel in high winds, heavy rain, snow, or when chain controls or incident restrictions are in effect.

Your actual move-time window comes from the permit itself; always review district-specific conditions and any temporary restrictions before departure.

Pilot/escort vehicles and high-pole requirements

Caltrans determines when escort (pilot) vehicles are required, based on route, roadway type, and the load’s dimensions. Requirements are listed on the permit and may differ across districts.

• Common triggers: One or more pilot cars are typically required for very wide loads (often starting around 12 feet on two-lane roads and around 14 feet on multi-lane routes), very long loads (commonly over 100 feet overall), or large rear overhangs (often 25 feet or more).
• Height pole: A lead escort with a calibrated high pole is commonly required when permitted height exceeds about 17 feet or when otherwise specified by the district, with a documented route survey.
• CHP escort: The California Highway Patrol may be assigned to escort “superloads” that significantly exceed routine permit thresholds or pose unusual operational risks.

Exact thresholds and the number/positioning of escorts are case-by-case and printed on the permit; do not rely on general rules-of-thumb over your issued conditions.

Marking, flags, signs, and lighting

Oversize loads must be conspicuous to other road users. Caltrans prescribes standardized signage, flags, and lighting to mark the load’s extremities and alert approaching traffic.

• Signs: “OVERSIZE LOAD” (or “WIDE LOAD”) signs are typically required front and rear when width or length exceeds legal limits. Signs must meet Caltrans size, color, and lettering standards.
• Flags: 12-inch (minimum) red or fluorescent orange flags must mark the widest points and any corners or projections. Rear overhang over 4 feet must be flagged in daylight and red lights at night.
• Lights: Amber warning beacons may be required on the vehicle and/or pilot cars. Night moves (if allowed) require proper lighting of the load extremities.
• Securement: All cargo must be secured per FMCSA Part 393 and CVC requirements; specialized securement may be mandated for specific commodities.

Your permit will list the exact marking and lighting required for the size, configuration, and time of travel; ensure equipment meets specification before you roll.

Weight limits and bridge compliance

California applies federal and state weight rules. Overweight permitting considers axle spacings, number of tires, and route bridges.

• Baseline limits: 80,000 pounds gross, 20,000 pounds single axle, 34,000 pounds tandem axle on Interstate routes (federal bridge formula applies). California’s state-network limits align but can differ in application off the Interstate.
• Permits: Overweight permits specify allowed axle-group weights by spacing and require approved routing to protect bridges and pavement.
• Combinations: Tridems and specialized axle groups are permitted by analysis; weights are set by the permit based on engineering review.

Never assume an overgross or over-axle move is legal without a written overweight permit and route approval; violations carry significant penalties and liability.

Where and how to get a permit

Caltrans issues state-highway permits through its Transportation Permits offices; cities and counties issue their own permits for local streets. Many carriers use permit services to coordinate multi-jurisdictional moves.

• Apply: Submit dimensions, weights, axle spacings, origin/destination, and proposed route. Provide a route survey for certain overheight moves as required.
• Types: Single-trip, repetitive, and annual permits are available for qualifying loads and corridors. Fees vary by type and complexity.
• Lead time: Routine permits can be fast; superloads and complex routes need engineering time and may require CHP scheduling.

Always confirm both state and local permissions for the entire route, including last-mile terminal access, before mobilizing equipment.

Local roads, ports, and special corridors

California’s state-highway permit does not cover city or county roads, port areas, or private facilities. Many local agencies publish their own rules, curfews, and construction restrictions.

• Local permits: Required when leaving the state highway to reach shippers, receivers, or staging areas.
• STAA terminal access: 53-foot trailers may use designated terminal access routes off the National Network; confirm local truck route maps.
• Construction zones: Temporary restrictions, lane closures, and detours can affect permitted routes; check current notices.

Coordinate state and local requirements to avoid dead-ends or violations during last-mile movements.

Enforcement, penalties, and liability

California enforces oversize rules through CHP and Caltrans, with penalties for operating without a permit or violating permit conditions.

• Citations and fines: Issued for oversize/overweight violations, missing pilot cars, improper signage/lighting, or route/time violations.
• Trip shutdowns: Loads may be detained until compliant; you may be required to re-route or wait for allowable hours.
• Liability: Damage to infrastructure or third parties can trigger substantial civil liability; permits do not transfer operator responsibility.

Keep permits on hand, train drivers on conditions, and document pre-trip checks to reduce enforcement risk and liability exposure.

Key references and authority

Oversize/overweight rules derive primarily from the California Vehicle Code (CVC §§35100–35796), Caltrans’ Transportation Permit Manual and district conditions, and applicable federal regulations for STAA routes and bridge formula compliance. Always rely on your current, issued permit and the latest Caltrans/local agency guidance for controlling details.

Summary

California treats any vehicle or load wider than 8’6″, taller than 14′, or longer/heavier than legal configuration limits as oversize/overweight, requiring a Caltrans transportation permit and strict compliance with route, timing, escort, and marking conditions. Permits are specific to your dimensions and route and often restrict travel to daylight, bar movement on holidays or during rush hours, and may require pilot cars or high-pole escorts for very large loads. Secure both state and local permits for the full route, follow all signage/lighting rules, and verify current restrictions before moving to stay safe and compliant.

What is the oversize law in California?

The California Vehicle Code requires an oversize load permit for any load exceeding legal weight or dimensions. That would be loads exceeding 14′ high (Section 35250), 8’6″ wide (Section 35100), 40′ long (single), 65′ (truck/trailer), 75′ (multi trailers) (Section 35400 & 35401), or 20,000 lbs/axle (Section 35550).

What is considered an oversized vehicle in California?

“Oversized Vehicle” shall mean any vehicle, as defined by Section 670 of the California Vehicle Code which exceeds twenty feet in length, seven feet in width, or eight feet in height.

What is the 40 foot rule in California?

The California 40-foot rule refers to the Kingpin-to-Rear-Axle (KPRA) distance limit for tractor-trailer combinations, which mandates that the rearmost axle of a semitrailer must be no more than 40 feet from the trailer’s kingpin. This rule, also known as the California Bridge Law, is a crucial component of weight distribution and safety for truck combinations within the state, affecting trailer configuration, axle placement, and overall weight limits to prevent overloading bridges.
 
What It Means for Truckers

• Axle Positioning: The rule requires truckers to position their trailer’s axles so the distance from the kingpin (where the trailer attaches to the tractor) to the center of the rearmost axle is 40 feet or less. 
• Weight Distribution: Proper KPRA alignment helps with weight distribution and prevents overloading specific axles and bridges, a key concern for California’s infrastructure. 
• Compliance: Violations can result in fines and detentions at scale houses, requiring load rework to comply with the KPRA law before continuing. 

How to Comply

• Measure Carefully: Use a tape measure to locate the rear axle center and the kingpin. 
• Adjust Axles: Slide the trailer’s tandem axles to ensure the rearmost axle is at or before the 40-foot mark from the kingpin. 
• Scale Loads: Even with a properly set trailer, weigh the truck at a scale to confirm axle and gross weights comply with California’s load limits. 
• Look for Indicators: Some trailers have stickers or markings on the side indicating the correct axle position for the 40-foot KPRA rule. 

Key Considerations

• Exceptions: While the basic rule is 40 feet, there are some exceptions for specific trailer types, such as semitrailers with a single axle, which have a 38-foot KPRA limit. 
• Weight Limits: The KPRA rule is closely linked to weight limits, such as the 34,000-pound maximum for trailer axles and the overall 80,000-pound gross vehicle weight limit. 
• Route Access: Be aware of the network of routes that allow for certain vehicle lengths, such as 45-foot buses and motorhomes, as not all roads accommodate these longer vehicles. 

What is the widest load allowed on a highway?

The widest load allowed on a highway in California without a permit is 8 feet 6 inches, but for loads exceeding this width, a permit is required, and the maximum width with a permit can be up to 15 feet, or even larger for a “superload” under special circumstances. The exact limits vary by state, and for wider loads, permits specify the exact route, and may require escorts and travel during certain hours only. 
Legal Limits

• Width: In most states, including California, a load is considered a “wide load” if it exceeds the standard width of 8 feet 6 inches. 
• Height and Length: There are also limits on height (often 14 feet in California) and length, which also trigger the need for a permit. 

Permits and Regulations

• Permits are required: for any load that exceeds the standard legal width, height, or length. 
• Superloads: Loads that are particularly wide (often 16 feet or more) or heavy are considered “superloads” and require more stringent permit processes. 
• Route Specifics: Permits detail the exact route that the wide load can travel. 
• Travel Restrictions: Permits may restrict travel to specific days of the week, daylight hours only, or prevent travel during peak traffic times, holidays, and weekends. 
• Escort Vehicles: Loads over a certain width (often 12 feet) require one or more escort vehicles to warn other drivers of the oversized load and to identify hazards ahead. 

Key Takeaway
The maximum allowed width for a load varies by jurisdiction. You must obtain a permit and follow specific regulations for any load that exceeds the standard legal width. For California, check the California Department of Transportation | Caltrans website for details on permit requirements and regulations.