OAKLAND -- When signaled over by a police officer while driving along Foothill Boulevard on Thursday morning, Jacky Chang was puzzled.
"I didn't know what happened. I thought maybe I had done something wrong," said Chang, of Oakland.
To his surprise, state officials wanted to check his gold Honda Accord to see if it complied with state emission standards.
The random smog checkpoint was set up last week by the state's Bureau of Automotive Repair, part of the agency's push to bring state air quality into compliance with federal standards. Other roadside stops in the Bay Area were set up earlier in the year in Antioch, Concord and the San Jose area.
California drivers can expect to see the emission checkpoints more often.
Random smog surveys have been conducted since 1985, but budget cuts trimmed the program to just one team in the field. The program received a financing boost in late 2011, so now two teams of inspectors are out on a near-daily basis -- one in Northern California and one in Southern California.
The goal of the inspections is to see what emissions are "actually like in the real world," and if the state's smog reduction programs are working, said Russ Heimerich, a spokesman with the Department of Consumer Affairs, which includes the automotive repair bureau.
Targeted at cars made from 1976 to 2007, the tests are voluntary. They are also not punitive, as drivers do not lose their licenses or rack up fines if they fail.
The tests, which take about 10 minutes, are set up similar to smog checks at a service station. Technicians drive the vehicle up onto an elevated metal dynamometer to check the car's components and systems, indicator lights, ignition timing, gas cap and exhaust recirculation system, said Eric DeBarruel, a program representative with the automotive bureau.
Technicians also perform a "tailpipe test," measuring exhaust emissions by inserting a probe into a vehicle's tailpipe.
"We tell the drivers that would have failed a test, why it failed and what repairs would be recommended," DeBarruel said.
Driver Jasmine Calip and passenger Destiny Anderson were among those frazzled that the tests would make them late -- Calip for an appointment and Anderson for class.
"This is not convenient for me," said Khansay Phoumivong of Oakland, who didn't mind having her car checked, but worried it would make her later for her job in Berkeley as a waitress.
Also, Phoumivong feared the test would mean she would have to get rid of her "older car," though she can't afford a new one.
Tests are set up in cities around the state almost every day, namely in urbanized areas with the poorest air quality and ZIP codes with more than 1,000 vehicles. Heimerich says the Bay Area has only a few days when its air quality does not attain quality standards, but the smog can get swept up by coastal winds and moved into the San Joaquin Valley.
"Our goal is to pick a random location so we can get as random a sample as we can get. We don't want to go to the same location twice," Heimerich said.
The checkpoint can't be on a one-way street and needs a place for people to pull their vehicles in and not impede traffic, he said.
The surveys also are a "check and balance" to make sure smog stations are doing adequate diagnostic tests and repairs, Heimerich said. Tests often confirm that there are a lot of cars on California roads where just enough repairs have been made for them to pass smog checks.
"After they pass, they go right back to polluting," Heimerich said.
Despite not being meant to punish drivers, officials acknowledge that the specter of seeing law enforcement directing traffic and pulling drivers over can be intimidating.
"There were a lot of drivers that were scared," CHP officer Erik Martinez said. "I spent a lot of time trying to calm them down."
"They certainly don't make it seem like it's voluntary. There were no warning markers. Nothing like that at all. It just seemed intimidating," said Mark Cutino of Brentwood.
Cutino did not have to stop at a January checkpoint on Antioch's Lone Tree Way, as officials waived him through after a quick scan of his plates.
Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.
For more information about the state's Roadside Emissions Survey program, go to the bureau's website at www.smogcheck.ca.gov.