For the purposes of these laws, "inoperable vehicles" are most often defined as those on which the engine, wheels, or other parts have been removed, altered, damaged, or allowed to deteriorate so that the vehicle cannot be driven. The following are some common conditions that cause vehicles to be in violation of these laws:
* Missing tires
* Vehicle on blocks
* Front windshield missing * No engine
* Steering wheel missing
* License plate with expired registration date
* No license tag

Emissions and Smog Check Programs
Many states operate their own I/M (inspection and maintenance) programs in areas that the EPA has designated as a "nonattainment area," meaning that the area has not attained the EPA's required air quality. The EPA checks for carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide when designating these areas and when an area does not meet the standard for any individual pollutant, or any combination of the pollutants, then it is placed on the list of nonattainment areas.

To meet the EPA's emissions reduction requirements, many states are implementing more stringent emission (I/M) programs. An I/M program may be currently operating in your state, or could be soon.

Policy makers must properly focus inspection procedures and not confuse legitimate aftermarket parts with emission defeat devices and tampering violations. The hobby must also pursue proactive legislative initiatives to establish exemptions from inspections for low-mileage vehicles, classic vehicles (defined as 25 years old and older), and newer vehicles. It is useful to remind legislators that the emissions from this small portion of the vehicle fleet are negligible. This is especially true when you consider the low miles typically driven by hobby vehicles and the excellent condition in which these vehicles are maintained.

Equipment Standards & Inspections
Understanding how vehicles and car parts are regulated can be a bit confusing. Here is a quick overview.

The Federal government, through the National Highway Traffic Safety Administration (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 prescribes the photometric requirements for a headlamp but does not dictate shape or size.

The FMVSS covers basic types of equipment (e.g., tires, rims, headlamps/taillamps, brake hoses, etc.) and establishes vehicle crashworthiness requirements (front and side impact, roof crush resistance, fuel system integrity, etc.).

Emissions and emissions-related parts are regulated by the U.S. Environmental Protection Agency (EPA) and various state agencies, primary of which is the California Air Resources Board (CARB). For products sold in California (and states that have adopted the California standards), manufacturers must conform to standards issued by the CARB.

Federal law prohibits states from issuing motor vehicle safety regulations that conflict with federal standards. This is called 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 "optional" or "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. State and local jurisdictions have authority to regulate inoperable vehicles or determine whether an enthusiast is engaged in a business vs. private activity. State and local law enforcement officials issue tickets and inspect cars.