San Benito County, CA Noise Ordinances: Vehicle Noise (2026)

Most vehicle-noise regulation in California is set at the state level and applies uniformly in unincorporated San Benito County, because the California Vehicle Code preempts most local rules about vehicle exhaust and equipment on public roads. The two core provisions are Vehicle Code Section 27150, which requires every motor vehicle to be equipped with an adequate muffler in constant operation and good working order to prevent excessive or unusual noise, and Vehicle Code Section 27151, which makes it unlawful to modify a vehicle's exhaust system in a manner that amplifies or increases the noise beyond what the original system produced, and prohibits 'gutted' mufflers, cutouts, and bypasses. California also historically sets maximum vehicle noise levels by weight class (the 95 dBA test standard is commonly referenced for vehicles under 6,000 pounds). These rules are enforced on public roads by the San Benito County Sheriff's Office and the California Highway Patrol, including on Highways 25 and 156 and the rural roads serving communities like Tres Pinos, Paicines, Panoche, and Bitterwater. Where vehicle noise is generated on private property rather than a public road - repeated engine revving, off-highway vehicles, or a vehicle audio system used as a stationary source - it can also be addressed under the County's Noise Control Regulations as a 'noise disturbance' under Section 19.39.020 and against the limits in Section 19.39.030. The County has not been shown to adopt a vehicle-specific decibel ordinance separate from the state code, so for on-road exhaust and muffler issues the Vehicle Code controls. Inside Hollister and San Juan Bautista, city police enforce the same Vehicle Code on city streets, supplemented by any city noise ordinance.