"The High Emitter Profile identifies the vehicles most likely to fail their Smog Checks. These vehicles are directed to Test-Only Stations for their initial testing.

source: California Bureau of Automotive Repair
 

In order to comply with the mandates of the federal Clean Air Act, the Department of Consumer Affairs/Bureau of Automotive Repair (DCA/BAR) began directing fifteen percent (15%) of all vehicles in Enhanced Areas to Test Only Stations in 1998. However, DCA/BAR has gradually increased the number of vehicles directed to Test-Only stations to continually improve program effectiveness and comply with the emission reduction objectives set forth in the State Implementation Plan, which is a master plan for complying with federal air quality requirements.

The majority of vehicles directed to Test Only stations are selected by application of the High Emitter Profile, which identifies the vehicles most likely to fail their Smog Checks.

High Emitter Profile. The High Emitter Profile (HEP) uses data from several different sources. Some of it comes from the state Vehicle Identification Database (VID), which collects data from Smog Checks transferred by modem during each individual test to the state VID and is used by the Department of Motor Vehicles, BAR, and other government agencies. In addition, general vehicle data such as make, model year, vehicle miles traveled, and engine size help define the HEP.

The vehicle data are sorted to determine which vehicles are most likely to fail their Smog Checks, especially at Gross Polluters levels—at least two times the emissions level allowed for the particular make and model of vehicle. While no single factor identifies a vehicle that is likely to fail, the data are weighted and vehicles are ranked from highest probability to the lowest depending on these data. Depending on the number of vehicles required in each county, the model begins selecting from the highest probability down the list to the number required for each county.

Two Percent Randomly Selected. As required by State law, two percent of the vehicle fleet in the Enhanced Areas that are subject to the Smog Check program are directed to Test-Only stations. These vehicles are selected randomly to evaluate the Smog Check program's overall effectiveness.

Motorist Notification. The Department of Motor Vehicles (DMV) notifies owners of vehicles which have been selected to have their initial Smog Check inspections performed at Test-Only Stations. The Registration Renewal Notice sent to these vehicle owners will say "Smog Certification Required at Test-Only Facility." If this statement is on your Renewal Notice and you take the vehicle to a test-and-repair station, the technician at the station will be unable to certify your vehicle. These vehicles must be inspected at a Test-Only Station."

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