The Southeast Michigan Council of Governments (SEMCOG) announced that they are going to be setting up drive by emissions test monitors over the next month. The monitors will be situated on highway ramps to measure the emissions of passing vehicles. Like red-light monitors, they will be equipped with cameras to photograph your car if you get a poor rating. If your car is spewing too much bad stuff, they'll send you a letter suggesting that you get your car checked out.
The machines will be out in the open and there will be a sign that tells you right away if you got a good, fair or poor rating. They estimate that only about one percent of cars will get a poor rating, but there will be no mandatory testing or repairs. This is strictly for information purposes and it would be interesting to see how accurate the results are.