U.S. ENVIRONMENTAL PROTECTION AGENCY EPA 400-F-92-016

OFFICE OF MOBILE SOURCES

FACT SHEET OMS-14

July, 1994

Clean Cars for Clean Air :

Inspection and Maintenance Programs

What is Inspection and Maintenance?

Inspection and Maintenance (I/M) is a way to check whether the emission control

system on a vehicle is working correctly. All new passenger cars and trucks sold

in the United States today must meet stringent pollution standards, but they

can only retain this low-pollution profile if the emission controls and engine are

functioning properly. I/M is designed to ensure that vehicles stay clean in actual

customer use. Through periodic vehicle checks and required repairs for vehicles

that fail the test, I/M encourages proper vehicle maintenance and discourages

tampering with emission control devices.

Why is I/M Needed?

Motor vehicle manufacturers have been required to meet increasingly stringent

new vehicle pollution standards. But vehicles that are poorly maintained or that

have malfunctioning emission controls often exceed those standards. Even

minor malfunctions can increase emissions while major malfunctions can cause

emissions to skyrocket. The average car on the road emits three to four times

more pollution than standards allow for new cars.

The percentage of dirty vehicles increases with age. Roughly 30 percent of

five-year-old cars emit excessive pollution. At seven years old, the average age of

passenger cars in the United States, 55 percent of vehicles are high emitters.

Overall, 10 to 30 percent of vehicles cause the bulk of the problem.

Unfortunately, it is not always obvious which vehicles fall into this category, as

the emissions themselves may not be noticeable and emission control

malfunctions do not necessarily affect vehicle driveability. Effective I/M programs can identify these problem vehicles and assure their repair.

I/M and Air Quality

Drivers may not think of their own vehicles as pollution sources, but cars and

trucks collectively are the single greatest contributor in this country to carbon

monoxide pollution and to ground-level ozone, the major component of smog. In

typical polluted cities, vehicles contribute between 35 and 70 percent of ozoneforming emissions and 90 percent or more of carbon monoxide emissions.
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Ambient concentrations of one or both of these pollutants exceed national air

quality standards in virtually every major urban area of the country.

Substantial reductions in vehicle emissions are essential in cities struggling to

achieve clean air. Depending on the sophistication of the program, I/M can

reduce vehicle-related hydrocarbon and carbon monoxide emissions by 5 percent

to more than 30 percent. A comprehensive I/M program can also yield reductions in nitrogen oxide emissions of up to 10 percent.

EPA oversees a number of programs designed to limit vehicle emissions,

including requirements for cleaner vehicles, cleaner fuels, and cleaner

transportation alternatives. Still, a well-designed I/M program remains the

single most effective and cost-effective way to achieve major reductions in vehicle

pollution.

What’s Involved in an I/M Test?

States design and operate I/M programs in accordance with national policy set

by EPA. In some states, inspections take place at government or privately-run

inspection stations that do not perform vehicle repairs. Other states license

service stations and repair shops to do inspections. Most states require annual

checks.

Two basic types of tests are performed in I/M programs. The first is a test of

emissions from the tailpipe (exhaust emissions). A probe is inserted into the

tailpipe while the vehicle is idling or while the engine is being revved to 2500

rpm. Emissions analyzers then measure pollution levels in the exhaust. The

second procedure involves a check to ensure that critical emission control

components are present and operational. Cars that fail because of dirty exhaust

or faulty emission controls must be repaired and re-inspected.

The cost to drivers for an I/M test varies from state to state and ranges from $5

in Arizona to $44 in California. The average test costs $8 in states with inspection-only programs and $18 in states where repair shops perform inspections.

Repair costs also vary considerably, depending upon the cause of failure. EPA

estimates the average bill nationwide to be about $50 to $70 per vehicle that

fails the test. The cost of some repairs is covered under emission performance or

defect warranties required by the Clean Air Act or under other manufacturer

warranties.

States consider vehicle design in setting the pass/fail cutoff for I/M tests. Older

vehicles are not held to the same standard as newer models with more sophisti
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cated emission controls. In addition, many states waive repair requirements if

the cost exceeds a predetermined limit.

I/M: What’s on the Horizon?

The 1990 Clean Air Act expands the scope of I/M as it currently exists. Many

cities will need to start new I/M programs over the next several years and some

cities that already require I/M testing will have to institute more comprehensive

emission checks. Specifically, the new law calls for either basic or “enhanced” I/

M programs in 154 areas, depending on the severity of pollution.

Basic programs will likely resemble those in place today with a simple emissions

test and check of emission control devices. “Enhanced” programs will involve

more comprehensive and sophisticated emission testing and functional checks.

For example, in addition to exhaust from the tailpipe, these programs will

address evaporative emissions, an increasingly important aspect of the

hydrocarbon pollution problem. The enhanced I/M provisions prohibit stations

that conduct I/M tests from performing vehicle repairs and also allows states to

take steps such as tightening enforcement procedures to increase the overall

effectiveness of their program.

Will New Technologies Eliminate the Need for I/M?

No, but emerging technologies may someday complement I/M programs:

• On-board diagnostic (OBD) systems will use vehicle computers to monitor

emission controls. The computer triggers a dashboard indicator light when the

controls malfunction. This, in turn, alerts the driver to seek maintenance for the

vehicle. Diagnostic systems will be required on vehicles beginning with 1994

models. Future I/M inspections will include OBD checks, but because the OBD

system itself could malfunction, be tampered with, or simply be ignored, OBD

will not be able to replace I/M.

• Remote sensing technologies are being refined that offer the potential for

a fast and convenient way to identify high-emitting vehicles. These technologies

take a “snapshot” of a vehicle’s emissions as it passes by a sensor located on the

side of the road. Like OBD, remote sensing could provide a useful addition to I/

M programs. The accuracy of remote sensing is still limited, however, and

remote sensing devices cannot measure evaporative emissions. Thus, an I/M

structure will still be necessary to ensure comprehensive and fair monitoring

and repair of all vehicles in a given area.
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For More Information:

The Office of Mobile Sources is the national center for research and policy on air

pollution from highway and off-highway motor vehicles and equipment. You

can write to us at the EPA National Vehicle and Fuel Emissions Laboratory,

2565 Plymouth Road, Ann Arbor, MI 48105. Our phone number is (313) 668-4333.

• Cleaner vehicle and fuel technologies required under the 1990 Clean Air Act

will help reduce emissions of tailpipe exhaust and evaporating gasoline. But cars

must be properly maintained and emission control systems must remain functional

if these reductions are to be fully realized. I/M serves as a continuing incentive for

motorists to have their vehicles serviced regularly.
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For Further Information:

To learn more about I/M programs in your area, contact your EPA regional office

(addresses listed below), or the motor vehicle or environmental agency in your

state.

Direct questions about I/M policy to the Emission Planning and Strategies

Division of the EPA National Vehicle and Fuel Emissions Laboratory, 2565

Plymouth Road, Ann Arbor, MI 48105.

Direct questions about warranty coverage of emission control components to the

Office of Mobile Sources Field Operations and Support Division, US EPA

(6406J), 401 M St. SW, Washington, DC 20460, or call 202-260-2633.

Region 1 CT, MA, ME, NH, RI, VT

U.S. Environmental Protection Agency

John F. Kennedy Federal Building

Boston, MA 02203

617/565-3225

Region 6 AR, LA, NM, OK, TX

U.S. Environmental Protection Agency

First Interstate Bank Tower at Fountain Place

1445 Ross Avenue, Suite # 1200

Dallas, TX 75202-2733

214/655-7214

Region 2 NJ, NY

U.S. Environmental Protection Agency

Air Programs Branch

26 Federal Plaza, Room 1034A

New York, NY 10278

212/264-2517

Region 7 IA, KS, MO, NE

U.S. Environmental Protection Agency

726 Minnesota Avenue

Kansas City, KS 66101

913/551-7494

Region 3 DE, DC, MD, PA, VA, WV

U.S. Environmental Protection Agency

841 Chestnut Building

Philadelphia, PA 19107

215/597-4554

Region 8 CO, MT, ND, SD, UT, WY

U.S. Environmental Protection Agency

999 18th Street

Denver, CO 80202

303/293-1754

Region 4 AL, FL, GA, KY, MS, NC, SC, TN

U.S. Environmental Protection Agency

345 Courtland Street, N. E.

Atlanta, GA 30365

404/347-3043

Region 9 AZ, CA, HI, NV

U.S. Environmental Protection Agency

75 Hawthorne Street

San Francisco, CA 94105

415/744-1177

Region 5 IL, IN, MI, MN, OH, WI

U.S. Environmental Protection Agency

Air and Radiation Division (5AD26)

Metcalf Federal Building

77 West Jackson

Chicago, Illinois 60604

312/886-7857

Region 10 AK, ID, OR, WA

U.S. Environmental Protection Agency

1200 Sixth Avenue

Seattle, WA 98101

206/553-1066