Principal Investigator: Dr. John Merrifield

Associate Professor of Economics

MRPI Faculty Associate



San Antonio is the largest US city with air quality in compliance with the Federal Clean Air Act. However, economic growth is jeopardizing San Antonio's attainment status. A non-attainment designation brings with it sanctions and new regulations that place significant burdens on regional economies. The designation is not easily removed.



Information and analyses from previous studies of environmental policy - including the author's owned published work - were combined with San Antonio's unique air quality situation. The air quality data came from the Texas Natural Resource Conservation Commission's (TNRCC) web site (



San Antonio is in serious danger of incurring the sanctions of a Federal Non-Attainment Area, but San Antonio does not have a general air quality problem. It has a ground-level Ozone problem on only a few days (so-called Ozone Action Days [OZADs]) during the warmer months. San Antonio had 26 OZADs in 1997, and 24 OZADs in 1998. However, the Ozone problem alone will cause San Antonio to 'achieve' non-attainment status in July, 2000 unless the all-important 4th highest 1999 eight-hour average ozone level is 81 parts per billion (ppb) or less. That's quite a challenge because the 4th highest reading was 84 ppb in 1997, and 90 ppb in 1998.

Stationary sources like factories and power plants are already subject to significant emission control requirements. The opportunities to realize significant cost-effective emission reductions beyond what the city is already doing at the city-owned, City Public Service power plants are extremely limited.

Stationary sources such as fuel transfer facilities (for example, gas stations) sometimes also produce evaporative emissions. City leaders are pursuing this source of air quality improvement through reformulated fuels. The increased use of reformulated fuels means that higher gasoline costs are incurred all the time (by someone, somewhere), but the resulting emission reductions have significant value only on each year's few Ozone Action Days (OZADs).

The lion's share of mobile source emissions comes from a relatively few, poorly maintained cars, especially the older, smoke-belching clunkers that are a familiar sight in San Antonio. Generally speaking, 10% of the vehicles (gross emitters) are responsible for over half of the key emissions, though the gross emitter share is probably larger in southern cities like San Antonio, where cars don't have to survive long cold winters.


The peak episode nature of San Antonio's air quality problem, and the sources of cost-effective opportunities to reduce emissions, boils down to this imperative: Minimize the time gross emitters are on the road on Ozone Action Days. Several effects will contribute to that objective.

What can/should be done to achieve one or more of those outcomes?

    1. Education
    1. Deploy remote emission sensing devices; they measure the emissions of moving vehicles.
    2. Prohibit the operation of gross emitters during critical periods (especially mornings) on Ozone Action Days (OZADs).
    3. Prevent the importation of gross emitters by requiring pre-1982 cars pass the emission test required semi-annually in Texas’ four non-attainment areas before they can be newly registered in Bexar County.
    4. Encourage the development of privately funded scrappage programs and low-income vehicle maintenance subsidy programs.
    5. Levy congestion tolls. Use the money to pay for administrative expenses, and to fund scrappage programs, subsidies for low income vehicle maintenance spending, and street/highway improvements.

The education component of the recommendations is critical. Without it there won’t be much support for unfamiliar practices and new expenses. For example, the public and their elected officials will probably see recommendation #3 as drastic and unrealistic unless they compare it to the effect of a non-attainment designation. In non-attainment areas, cars that fail the more demanding (compared to the remote sensing device) I&M inspection cannot use their vehicle on ANY day. There will have to be some hardship and emergency waivers, but exceptions to the OZAD gross emitter ban should be extremely rare. A liberal waiver policy is a terribly costly way to subsidize low income families. Subsidies, if any, should assist them to avoid violations; that is to buy and maintain vehicles that are not gross emitters.

During OZAD critical periods, the remote sensing devices are used to levy fines for violations of the gross emitter ban. Notices generated on non-OZADs should alert drivers of gross emitters of the new ordinance, the need for repairs, and public transportation options.

The proposed congestion toll is another example of a policy that will have the popularity of a migraine headache unless it is preceded by a well-designed education campaign. Properly implemented congestion tolls are very cost-effective ways to cut emissions. The intended effect of the toll is to shift the most discretionary travel to less congested times and places. Properly targeted congestion tolls are cost effective even without their considerable air quality benefits. The benefits of conserving fuel, saving motorists' time, and reduced road capacity requirements are enough to justify properly targeted tolls. Motorists will gradually realize that they spend less time in traffic jams, and that they spend less money on fuel and vehicle maintenance. For that reason alone, the public may eventually support the use of congestion tolls on the basis of congestion problems alone; that is not limit their use to OZADs. However, because of the initial antagonism factor, congestion toll use should begin limited to the OZAD critical periods.

The recommended actions are relatively inexpensive and un-intrusive (definitely true relative to what is required in non-attainment areas), and as a package, they are probably self-funding without a general tax increase. The air quality enhancement expenses include:

The funding sources include:

A non-attainment designation will adversely impact many businesses directly, including non-emitters. That fact should be used to increase the incentive for businesses to fund some air quality enhancement programs on their own. They include programs that purchase and retire gross emitters, and programs that help low income families pay for vehicle maintenance, or vehicle replacement.

If those recommendations are implemented quickly, there is a good chance that San Antonio can stay in compliance with the Federal Clean Air Act. If they are not implemented quickly, San Antonio will soon become Texas’ fifth non-attainment area.