Emissions testing has been a controversial subject ever since its inception. Though most opinion polls show widespread public support for clean air in general, few motorists show any enthusiasm for emissions testing when it involves their own vehicles. And most are reluctant to spend money on emission-related maintenance or repairs.

POLITICS VS. TECHNOLOGY
At a recent clean air conference sponsored by the National Center of Vehicle Emissions Control & Safety (NCVECS), Colorado State University, a variety of speakers addressed the various issues confronting emissions testing today:

Little political or public support for emissions testing.

Lax standards and poor enforcement of existing I/M programs.

Lack of credibility that existing I/M programs are having an impact on air quality.

Reluctance to implement effective enhanced I/M programs in non-attainment areas.

Political pressure on the EPA to be more "flexible" in accepting various emission testing alternatives.

Rising costs of administering and conducting enhanced emissions testing.

Less need to inspect newer vehicles.

Adding OBD II checks into existing I/M programs, or substituting OBD II checks for tailpipe tests on 1996 and newer vehicles.

Technician training and competency.

LOOKING BACK
In 1990, Congress amended the Clean Air Act. The revisions required areas that did not meet national ambient air quality standards (NAAQS) to implement either basic or "enhanced" vehicle I/M emissions testing programs, depending upon the severity of the area's air quality problem. The act also required that metro areas with populations of more than 100,000 implement enhanced I/M emissions testing regardless of their air quality designation. EPA, in turn, was required to develop standards and procedures for emissions testing.

On November 5, 1992, EPA issued its original rule establishing minimum performance and administrative requirements for states developing air quality implementation plans. The EPA said areas that needed enhanced emissions testing would have to use their new "I/M 240" test procedure. I/M 240 was controversial for several reasons. One was that it specified centralized testing. The EPA said the use of "test only" facilities administered by an independent contractor would eliminate any conflicts of interest (fraud) in shops that both test and repair vehicles. California garage owners balked at the requirement, and eventually forced the EPA to accept a hybrid decentralized program in their state.

The I/M 240 requirement also specified loaded mode testing for measuring transient emissions on a special dynamometer, as well as checking NOx emissions and doing an evaporative system purge and pressure test. The I/M 240 test was based on procedures the EPA had already developed for certifying new vehicle emission compliance. This, in turn, required a lot of expensive equipment as well as the use of a trained operator to follow a prescribed drive cycle while the vehicle was on a dyno.

In 1995, however, the National Highway System Designation Act was passed. The act included provisions that specifically barred the EPA from mandating I/M 240 exclusively for enhanced emissions testing. So the EPA was forced to adopt a more flexible posture toward alternative I/M test programs. States are still required to meet air quality standards, but now have a much wider range of options for meeting those standards. These include scrapping programs for taking older vehicles off the road, the use of onboard diagnostic system (OBD) testing for verifying emissions performance, the use of decentralized I/M programs, roadside testing and various enhanced test procedures such as acceleration mode testing (ASM) and others that have been developed as alternatives to I/M 240.

For example, it is currently possible for some areas to design programs that meet the required enhanced I/M performance standard without any tailpipe testing at all, using a combination of alternative evaporative system pressure testing methods, onboard diagnostic system checks, and visual anti-tampering inspections.

Many states are now looking at a process called "clean screening" to simplify emissions testing. The goal here is not to identify high polluting vehicles for repairs, but to identify especially clean vehicles, which can be exempted from routine testing. Some states now exempt new cars from emissions testing until they are four or five years old, and then only require testing every two to three years thereafter.

CURRENT STATUS OF ENHANCED EMISSIONS TESTING
So what has happened to I/M 240? It got off to a poor start in Maine in 1995. The state and repair industries were both ill-prepared to handle the rigors of enhanced emissions testing and the repairs generated by the failures. The public outcry that followed forced the governor to cancel the program. The state is currently doing only a gas cap pressure test and visual inspection of the catalytic converter. OBD testing will begin in January 2000.

Colorado was the next to adopt a modified I/M 240 program, also in 1995. But critics of Colorado's program cite a study by the Colorado Dept. of Public Health and Environment that found the state's I/M 240 program had virtually no impact on air quality. During the program's first year of operation (1995), ambient carbon monoxide levels were actually worse than the five previous years, and showed no reduction in median CO levels over the five-year period.

Other states that have implemented some type of enhanced emissions testing (I/M 240 or similar tests that check emissions during transient operating modes on a dyno, or acceleration simulation mode (ASM) tests that check emissions while the vehicle is under a steady-state load on a dyno) include Arizona, California, Connecticut, Georgia, Illinois, Indiana, Maryland, Massachusetts, New Jersey, New York, Ohio, Oregon, Pennsylvania, Virginia, Washington, Wisconsin and the Washington D.C.

Rhode Island is slated to implement a 93-second version of I/M 240 in January 2000, followed by Missouri in April.

What is interesting to note is that Michigan, the car capital of the world, has no emission testing program of any kind, not even a visual inspection.
EMISSIONS TESTING FUTURE
By 2005, some experts say the need for basic or enhanced tailpipe emissions testing will be much less than it is today because the majority of vehicles on the road will have OBD II. Instead of checking tailpipe emissions, a simple OBD check with a scan tool will be all that is needed to verify emissions performance. Based on current projections, tailpipe emission checks will probably be needed for older cars and trucks until 2010, but by 2025 tailpipe checks will no longer be needed (if not before then!).

The direction that I/M takes in the future will depend on the findings of a National Academy of Science study on the impact of I/M programs on air quality. (May 2000). The report showed minimal impact, giving extra ammunition to those who oppose expanding enhanced emissions testing programs.

The EPA is currently working on a new standard for enhanced emissions testing called I/M 147, which may eventually replace I/M 240 and other enhanced test procedures. The EPA is also developing a "module 6" test procedure for purge testing vehicle evap control systems on pre-OBD II vehicles. At the same time, EPA procedures for evaluating ambient air quality (one-hour average ozone reading versus eight-hour average reading) are also under review and may undergo some changes. This, in turn, would have an impact on whether or not an area meets air quality standards, and if not, what steps they might have to take to meet those standards.

As the vehicle population continues to get cleaner, and new vehicles meet even low emission vehicle (LEV) and ultra-low emission vehicle (ULEV) standards, the cost of I/M programs will likely come under close scrutiny by legislators. Some areas may opt to phase out their annual or biennial emissions inspections and replace them with OBD checks, roadside sniffers and profiling to zero in on problem vehicles.

EVAP Evaporative Emission Control System

Driveability Diagnosis: Misfires
Finding & Fixing Vacuum Leaks
Understanding Oxygen (O2) Sensors
Wide Ratio Air Fuel (WRAF) Sensors
Sensing Emission Problems (O2 Sensors)
Evolution of I/M 240

Sensing Emission Problems (O2 Sensors)
Decoding Onboard Diagnostics
TROUBLE CODES (list of generic OBD2 trouble codes and definitions)
All About Onboard Diagnostics II (OBD II)
Understanding OBD II Driveability & Emissions Problems
Zeroing in on OBD II Diagnostics
OBD II Emissions Testing
Evolution of I/M 240
The Environmental Challenge Now Is CO2