"Test-Only Station" Explained

What's a Test-Only station? TestOnly stations are smog-test facilities that aren't connected to any kind of repair shop. They don't make repairs and they don't refer motorists to specific repair locations; their sole purpose is to conduct the smog-test procedure. In an effort to more accurately test the emissions systems of California's rolling stock and cut down on the number of failures that slip through the cracks, the Bureau of Automotive Repair established these TestOnly stations. As of 1 July 2004, 36% of cars in what the State calls "enhanced areas" are required to provide their bi-annual smog check at a TestOnly station. The Bay Area has been deemed an enhanced area by the

Environmental Protection Agency - that is, an area of the state that suffers from severe air pollution.
  This Test-Only percentage is made up of a combination of High Emitter Profile vehicles (cars that have abnormally high mileage, low mileage, or a history of emissions recalls or technical service bulletins) as well as randomly selected renewals. The test procedure and equipment are identical to that of smog checks offered by facilities that make repairs. If the car fails, the TestOnly station will retest the car for free once the repairs have been made.
  In July of last year, the smog-testing procedure changed to include a dyno test.

Today, cars are tested with the wheels rolling and the engine under load, which simulates actual driving more accurately than free-revving the car while it sits still. Since four-wheel dynos are exceedingly rare, all-wheeldrive cars (such as Carrera 4s) still take the old-fashioned static test.
  The State has structured the smogcheck process with the goal of catching cars with emissions-system problems whether or not they pass at the tailpipe. To accomplish this, the new test is performed in a strict order: The dyno run and tailpipe-emissions check are done first, followed by a visual inspection and finally a functional inspection. As a result, a car with passing tailpipe emissions but an illuminated check-engine light will fail, since the tester must check the light as part of the functional inspection. Likewise the gas cap must seal, and so forth.
  Tony's best hint? Before your smog check, always warm up the car and drive it normally for about 15 minutes. Studies have shown that cars that are driven for at least 10 - 15 minutes before testing are more likely to pass than those that are tested cold.