Cal. VEH § 521
This is the official text of Cal. VEH § 521, part of California’s Vehicle Code — governs traffic laws, driver's licenses, and vehicle registration.
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Official statutory text
A “retarder” is a device, other than a brake, which, when activated by the driver, applies a retarding force to the wheels of a vehicle without the use of friction. A retarder may be installed in or on the engine, exhaust system, drive train, or wheels of a motor vehicle, or an axle or wheels of a towed vehicle. A retarder may operate by altering the valve timing of the engine, by controlling the flow of a circulating fluid, by applying an electromagnetic force, by controlling the release of gases from the exhaust system, or by other means. A retarder may or may not be capable of stopping the vehicle upon which it is installed.
Status: in_force · Read it on the official government site
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