Sensors to Help Find High-Polluting Cars : Environment: Roadside devices use an infrared beam to gauge emissions. Worst offenders could be pulled over or receive notices.

In a state campaign to step up the battle to catch exhaust-belching cars, infrared sensors will be set up along roadways throughout California beginning next month.

Mounted in a parked van, the equipment sends an infrared beam across a lane of traffic to measure hydrocarbons, carbon monoxide and carbon dioxide emitted by a passing car. The results are shown to drivers on flashing signs, and license plates are captured on high-speed video so state officials potentially can take action against the worst polluters.

Despite concerns over accuracy of the technology, the remote sensors are becoming a key component of the state’s newly revamped Smog Check program.

Beginning in mid-September, 10 monitors will be deployed throughout the state, including seven between Ventura and San Diego. Over the next three years, the number is expected to triple. Locations, which will frequently change, have not yet been selected.

The state Bureau of Automotive Repair demonstrated the roadside tests in Los Angeles on Wednesday to kick off a campaign to familiarize the public with them.

K. Martin Keller, the agency’s chief, said the tests will be a deterrent to those who maintain their vehicles poorly or tamper with their emission-control devices.

Motor vehicles contribute more than half of the smog-forming gases in the Los Angeles Basin, and about 10% of vehicles cause about 40% of that pollution, air quality officials say.

“The bulk of people feel they are paying in deteriorated health for the sins of a small group of people who are essentially scofflaws,” Keller said.

The California program will be the “first full-scale, real-world implementation” of the roadside technology, said Doug Eisinger, chief of the U.S. Environmental Protection Agency’s regional mobile sources section.

“There aren’t many of these remote sensors in use across the country or anyplace else,” he said. “It is clearly an emerging technology.”

The point, Keller said, is to bolster California’s biennial smog inspections by switching the focus from simply obtaining a certificate to actually repairing the worst-polluting cars. Studies have shown the current program is plagued by fraud and testing errors.

Also as part of the Smog Check overhaul, some cars will soon be sent to special testing centers instead of service stations for inspections.

The long-awaited changes in Smog Check have taken five years because of a feud between the federal government and state Legislature over the best way to identify cars with excessive exhaust.

The monitors--which flash drivers a reading of “poor,” “fair” or “good” emissions--will most likely be set up along high-traffic, one-lane spots with a fairly even slope--such as freeway on-ramps.

When a vehicle drives through the infrared beam, the detector takes dozens of measurements of the exhaust in less than a second. The more infrared light a car’s exhaust absorbs, the dirtier the emissions.

Since each sensor is capable of 500,000 readings per month, as many as 3.5 million cars could be tested in Southern California each month, Keller said.

Wednesday’s demonstration at a site off Crenshaw Boulevard showed that the oldest cars are not necessarily the highest polluters. One mid-1980s model had emissions five times greater than a 1965 car that sailed through with a “good” reading.

State officials say if a car flunks multiple readings--the exact number has not yet been decided--its owner will be required to go in for a full smog check. Only cars with exhaust gases that are five times greater than emission standards will be sent notices or immediately pulled over.

Kelly said the state is trying to avoid an intrusive, heavy-handed program by targeting only the dirtiest cars. No action will be taken against cars that flunk the roadside tests during the initial few months.

“I’d like to err on the side of caution so there is confidence in the technology,” Keller said.

Previous tests have shown the devices can be highly inaccurate under some conditions.

In a pilot project in Sacramento last year, the equipment identified only 10% of the vehicles with high emissions. And 58% of ones that registered as high emitters turned out to be false readings, according to Sierra Research Inc., a consulting firm that reviewed results of the state study.

The inaccuracies could have been caused by a poor selection of sites because emissions are uncharacteristically high if a vehicle is accelerating or driving up a steep slope.

“It’s a neat technology that can really help clean up the air if used appropriately,” said Richard Sloan, a consultant for a firm that manufactures the devices. “All eyes are on California to see what happens.”

Other experiments have had more accurate results, including recent tests in Santa Ana and Costa Mesa conducted by the South Coast Air Quality Management District, said AQMD Chief Scientist Alan Lloyd.

“It’s certainly not a panacea,” Lloyd said, “but it is certainly a very helpful tool in identifying one of the causes of on-road emissions. Like many technologies, they are perfected over a period of time.”

The roadside tests have also raised socioeconomic concerns because many high-polluting vehicles, especially in the Los Angeles area, belong to low-income people who cannot afford to fix their cars or buy new ones.

“We’re trying to do this with as much community sensitivity as we can,” Keller said. “But in the real world, there will potentially be a lot of problems.”

The state Legislature and the EPA fought for years over how to revamp California’s Smog Check program.

The EPA preferred that all vehicles be inspected at 200 state contractor-operated facilities and then repaired, if necessary, at private service stations. But state legislators wanted to retain the about 9,000 service stations that conduct both tests and repairs, a $480-million-a-year industry.

The EPA and the state finally agreed on a compromise that combined both elements and added the use of remote sensors.

Each year, 15% of cars in the state’s smoggiest regions will be sent to the test-only sites and the rest will still go to service stations. Keller said the centers will open this year in Sacramento, but it could be two years before they are opened in the Los Angeles Basin.

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Living With Smog

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