For the marker rule, measure from the taillamps to the extreme rear of the load. For the maximum rear projection, measure beyond the last point of support.
At 4 ft or more behind the taillamps: one flag or cloth at least 18 in square for a load 2 ft wide or less; wider loads require two marking the maximum width.
At 4 ft or more behind the taillamps: two red lights, visible at least 500 ft to the sides and rear, in addition to required vehicle lamps.
The rear load generally may not extend beyond the last point of support by more than two-thirds of the wheelbase. Overall-length and special-load provisions can also apply.
The boundary wording matters
California's marker trigger is “four feet or more,” so exactly 4 ft triggers the rule. Do not substitute an open tailgate or bed extender for the taillamp reference point in that marker measurement.
A visibility marker does not by itself make a setup legal. Maximum projection, total length, securement and exceptions remain separate checks.
Checks the calculator cannot finish for you
- Calculate the two-thirds-of-wheelbase rear limit from the last point of support.
- Confirm overall vehicle/load length, width, securement and route limits.
- Review special provisions for poles, timber, pipe, structural materials and other listed loads.
STATE PRESELECTED
Measure the actual setup, then review the rule result.
The calculator keeps unsupported cargo length separate from the legal projection named by the state rule.
Open with California selected →OFFICIAL SOURCES
Rule information was last checked on Aug 16, 2026. Official pages and current law control if this summary differs.
Caltrans overhang guidance · CVC §§ 35410, 35411 and 24604 ↗