(Bloomberg) -- Each year, millions of American motoriststrudge to state inspection stations to make sure their vehiclesaren’t violating pollution limits.

At least, that’s what they think they’re doing. As theemissions-cheating scandal involving Volkswagen AG demonstrates,the tests may not be all they are cracked up to be.

“The Volkswagen scandal underscores some huge flaws in theemissions test systems we have in the real world,” said FrankO’Donnell, president of Clean Air Watch, a Washington-basednonprofit. “Dating back to the 1990s, the car inspection tests havebeen pretty flimsy.”

VW is currently negotiating with the U.S. EnvironmentalProtection Agency and California regulators on how to fix the600,000 cars on the road so they can order a recall. A federaljudge in California has ordered the sides to come to some agreementby Thursday.

Meanwhile, critics are calling for the 32 states that mandateemissions tests to close loopholes and make them harder togame.

State tests

While the EPA certifies each model of vehicle before it can be soldin the U.S., it’s left to the states to make sure each individualcar and truck on the road meets standards. But most states don’teven bother with diesels. And the tests for gasoline enginesgenerally just check a car’s software to see if the pollutioncontrol systems are in working order.

That’s precisely what VW rigged.

The EPA has even gone so far as to assure VW owners not to worryabout passing state inspections. The carmaker’s illegal software“was specifically designed to ensure that vehicles would passinspection,” the agency says on its website.

“I don’t necessarily mind bringing my car to emissions, but itdoes seem strange that diesel cars are exempted, especially afterwhat happened with VW," said Lauren Cooper of Takoma Park,Maryland. "I think the system should be re-evaluated.”

Hassles

Cooper made the mistake of taking her elderly mother’s 2011 HondaCivic in for an oil change before the test. That wiped out thecar’s computer codes. After waiting in line for 25 minutes on aSaturday, Cooper was told to drive the car around for 10 days andtry again.

“I had no idea,” Cooper said. “We should be informed that you’renot to have your vehicle serviced before bringing it in.”

To critics like Donald Stedman, a chemistry professor at theUniversity of Denver, the whole emissions testing system is missingthe point — which should be to find the worst polluting carsand get them off the road. States, under orders from the federalgovernment, are spending most of their resources looking at carsunder idealized conditions. They have little idea which vehiclesare spewing high levels of pollution in the real world.

Related: VW may be forced to clean the air its diesel carspolluted

“The VW scandal shows the government testing programs areirrelevant,” Stedman said. “What matters is what the stupid carsare doing on the road.”

Regulators found this out the hard way. Technology installed inVolkswagen 2-liter diesels since 2009 and in certain 3-literdiesels since 2014 turns emissions controls on only when thevehicle senses it’s being tested. In regular driving, the systemsturn off, which boosts engine performance and fuel economybut permits up to 40 times the legal limit of pollution.Software that does that is known as a "defeat device."

State emissions tests aren’t meant to catch corporatecheating, they’re trying to flag the most common type ofmaintenance issues that make metropolitan air qualityworse. (AP Photo)

Worsening pollution

State testing programs were established in the 1990s at theinsistence of the EPA to combat worsening air pollution in thelargest U.S. cities. That federal mandate caused resentment instate capitals, and in many cases that led to testing systems witha lot of loopholes, said O’Donnell of Clean Air Watch.

Some states formerly used equipment to measure what’s coming outof the tailpipe. Now an attendant typically lifts the hood andhooks a computer-code reader into a car’s on-board diagnosticsystem. That’s a processor connected to the vehicle’s variouscomputer systems that will register if equipment isn’t working asdesigned.

As long as the pollution controls are working as designed, avehicle will pass.

Some states exempt older cars, or even newer ones under thetheory that it takes awhile for pollution controls to go wrong. Andin at least one state, North Carolina, a car gets a pass if repairsto fix the emissions would cost more than $200.

Pollution controls

The tests are designed to ensure that pollution controls areworking as they’re engineered to do. If they’re designed to cheatthe tests, as in the case of Volkswagen, they’ll pass, saidMichelle McVay, a spokeswoman for California’s Department ofConsumer Affairs, which operates the state’s Smog Check system.

In California, cars made in 1999 and earlier model years havetests that use probes to measure what’s actually coming out of thetailpipe. The current equipment isn’t capable of reading dieselemissions, McVay said.

“The difficult part of this dilemma is that all of these VWvehicles with the defeat devices would pass the certificationtesting at any time, so it is believed they would also pass a SmogCheck emissions test at any time,” McVay said.

State emissions tests aren’t meant to catch corporate cheating,they’re trying to flag the most common type of maintenance issuesthat make metropolitan air quality worse, said Rob Klausmeier, anAustin, Texas-based emissions-testing consultant who has workedwith several states.

One thing states could do is adopt a technology calledremote sensing, which can passively measure emissions from vehiclesas they pass on the road. Colorado and Virginia already useremote sensing to supplement their inspection and maintenancetests. (AP Photo)

Efficient system

Gasoline-powered cars represent the vast majority of personalvehicles on the road, so state systems concentrate mostly on them,Klausmeier said. The basic thing that can go wrong with gas cars isa failing catalytic converter. The state tests are an efficient,cheap way to catch that.

“The tests did what they were supposed to do,” Klausmeier said.“They could do in-depth testing on each vehicle, but it would costmore and could be quite onerous.”

Changes are afoot in California, where officials at the state’sAir Resources Board have proposed expanding and refining the amountof data collected from car computer systems, according to DaveClegern, an agency spokesman. The board will be monitoring CO2emissions in real time, he said. In the future, CARB could expandreal-time data collection to include NOx, soot and otherpollutants.

The state has stepped up its efforts to catch automakercheating, but those efforts have focused on adding road tests toits compliance testing rather than what’s done at theinspection-and-maintenance station.

Additional tests

“Once we determined there was some kind of anomaly with the VWsystem our scientists and engineers were able to create additionalcycles and test approaches to challenge the cars and replicatestreet conditions, and we could see the point at which the NOxsystem was being bypassed,” Clegern said. “This type of improvedtesting is where we expect to go in the future.”

EPA expanded its reviews of new models to include on-roadtesting in September 2015. The agency is constantly looking at newinformation to reevaluate its approach to compliance and oversight,according to Laura Allen, an agency spokeswoman.

“We continue to review the information before us and will beworking with our partners, including states, to ensure that theAmerican people get the emissions reductions promised under theClean Air Act,” Allen said.

One thing states could do is adopt a technology called remotesensing, which can passively measure emissions from vehicles asthey pass on the road. It’s a kind of pollution surveillanceprogram that would have caught VW years before the EPA andCalifornia did, said Lothar Geilen, chief executive officer of OpusInspection Inc., an East Granby, Connecticut-based supplier ofremote sensing systems.

Colorado and Virginia already use remote sensing to supplementtheir inspection and maintenance tests. Vehicle owners whose carspass the on-the-road checks get passes to skip the trip to theemissions station.

“Our laws and regulations have focused too heavily on thelaboratory,” Geilen said in a statement. “We are incentivizingmanufacturers to calibrate performance to the laboratory test.”

Related: Renault plans 15,800-car recall to fix faultypollution filter

Copyright 2018 Bloomberg. All rightsreserved. This material may not be published, broadcast, rewritten,or redistributed.