Ironically, most custom-fabricated equipment is stronger and better designed than many OEM
Equipment Standards & Inspections
We're certainly not against proper quality and performance standards; no one wants poorly engineered, dangerous parts on their car. Understanding how vehicles and car parts are regulated can be a bit confusing, however. The simple explanation is that the federal government, through the NHTSA, has the right to set, enforce, and investigate safety standards for new motor vehicles and motor vehicle equipment. These Federal Motor Vehicle Safety Standards (FMVSS) are performance-based; they do not dictate design elements. For example, the federal lighting standard describes the photometric requirements for a headlamp, but does not dictate shape or size. The FMVSS covers basic types of equipment like tires, rims, headlamps and taillights, brake hoses, and more, and establishes vehicle crashworthiness requirements for front and side impact, roof crush resistance, and fuel system integrity to name a few.
Emissions and emissions-related parts are regulated by the EPA and various state agencies, primarily CARB. For products sold in California (and states that have adopted the California standards), manufacturers must conform to certification processes established by CARB. For those seeking CARB exemption status, SEMA has even created the Black Book, which explains the requirements and identifies ways to minimize both cost and time in reaching compliance status. That's especially useful since a CARB EO number usually qualifies the part for 50-state legality.
Federal law prohibits states from issuing motor vehicle safety regulations that conflict with federal standards, referred to as federal preemption, however, states are free to enact and enforce safety and equipment regulations which are identical to the FMVSS or, in the absence of a federal rule, establish their own laws and regulations. The most frequent examples of individual state rules cover parts like accessory lighting equipment, noise levels for exhaust and stereo systems, suspension height, and window tinting. States also establish rules on how a vehicle is titled and registered, and they have authority to regulate inoperable vehicles or determine whether an enthusiast is engaged in a business versus a private activity.
While some laws are better than others, there is a constant need to remind state policy makers not to be biased in favor of the vehicle's original equipment, such as lighting, tires and wheels, suspension components, and bumper/frame height. Opposing arbitrary and unnecessarily restrictive equipment and inspection laws is a constant challenge, and that's where SEMA and SAN come in. They're working on both the state and federal level to ensure your ability to lift or lower your rod, swap the suspension, or otherwise use aftermarket parts to tailor your car for its intended use.
States that have quantifiable noise standards on the books are shaded red in the map above
Exhaust: How Loud is Too Loud?
Most hot rodders can agree that exhaust shouldn't be obnoxiously loud, but the problem is that loud is subjective, and vague legal language doesn't set a clear and objective standard for aftermarket exhaust. On exhaust noise levels, states can generally be divided into two major categories: those with quantifiable noise standards and those without. Often those with regulations are not properly enforced because they are based on noise measured while a vehicle is in motion on the highway, usually from a distance of 50 feet from the center lane of travel. Typically, vehicles are divided into classes and decibel standards are set-one for driving on roads with a speed limit of 35 mph or less, and a second for driving on roadways with a speed limit greater than 35 mph. Other states choose not to specify a quantifiable noise standard and simply prohibit "excessive or unusual noise." But who's to say where that level is?