California’s 55 mph Truck Limit and Right-Lane Rules

A 65 or 70 mph freeway sign does not override California’s 55 mph maximum for vehicles covered by California Vehicle Code section 22406. Common commercial-truck categories include motortrucks or truck tractors with three or more axles and any motortruck or truck tractor towing another vehicle. A two-axle straight truck is not automatically covered merely because it has commercial plates, a USDOT number, or a CDL driver, but towing may bring it under section 22406.

For a covered vehicle, 55 mph is a maximum, not a target. A lower posted limit controls, and California’s Basic Speed Law may require a slower speed when weather, visibility, traffic, road surface, or roadway width makes 55 mph unsafe.

Lane choice begins with roadside signs. If signs designate lanes for section 22406 vehicles, the driver must use them. Without a designation, the default is the right-hand traffic lane. On a divided highway with four or more clearly marked lanes in one direction, a covered vehicle may also use the adjacent lane. Only lanes in the current direction count. Even on a five- or six-lane freeway, the rule generally concerns the two far-right lanes.

Passing does not expand the permitted lane range or suspend the 55 mph limit. A covered vehicle may pass within the designated lane, the right-hand lane, or the lane immediately to its left. The statutes do not create a general right to use a third or farther-left lane. After passing, return to a permitted lane.

Drivers may use another lane when preparing for a turn, entering or exiting a highway, or when necessary to continue the intended route. That exception supports a specific maneuver or interchange movement; it is not general permission to cruise in farther-left lanes. Slower-traffic rules and two-lane turnout requirements may also apply separately.

An ordinary right-lane restriction is different from a truck-only lane. Caltrans currently identifies truck-only facilities at the I-5/SR-14 split and at the southbound I-5/SR-99 junction near the Grapevine. Drivers should rely on the vehicle combination, posted limits, regulatory signs, lane markings, same-direction lane count, and the maneuver underway.