it seems to us that there must be some cost/benefit implications when a single remote sensor can measure tailpipe emission from 58,063 vehicles, without inconveniencing the drivers, during the same time period that two teams can do 307 traditional inspections and EPA can carry out 80 of their new test.

Figure 2. Each of the ten bars has a height that matches the average CO emissions of 10% of the cars in Denver.

In Colorado, the entire $40 million Envirotest testing facility, 15 stations with 54 lanes, measures 4,000 vehicles per day (Rocky Mountain News, March, 1995). A single remote sensor can measure more!

With so many cars easily measured, we started to look into the statistics. To our surprise, our data, Federal Test Data, indeed all the data we could find showed half the pollution from less than 10% of the vehicles. These vehicles we call gross polluters. Figure 2 shows 10 bars whose height matches the average CO emissions of 10% of the cars in Denver. Notice how much higher emitting are the gross polluters than the majority of the cars. Very few new cars are gross polluters (about 2% of two-year-old cars), but even among the oldest cars (1974 and older, all without catalysts) the majority (60%) are not gross polluters.