According to the California Air Resources Board, the California Smog Check program removes about 400 tons of smog-forming pollutants from California’s air every day.
On March 12, 2009, the Bureau of Automotive Repair and the Air Resource Board hired Sierra Research, Inc. to analyze the data collected in the BAR’s Roadside Inspection Program to evaluate the effectiveness of the Smog Check Program from data collected in 2003–2006. Under the Roadside Inspection Program vehicles are randomly inspected at checkpoints set up by the California Highway Patrol (CHP). One objective of the evaluation was to compare the post smog check performance of pre-1996 (1974–1995) vehicles to the post smog check performance determined from a previous evaluation collected in 2000–2002.The report made several recommendations to reduce the number of vehicles failing the Roadside test. One was to develop a method for evaluating station performance. The other was to perform inspections immediately following certifications at smog check stations. Finally, the report recommended continued use of the Roadside test to evaluate the effectiveness of the Smog Check program.