From the Texas Commission for Environmental Quality:
How Reporting Works
You can help the TCEQ get the word to owners of smoking vehicles in Texas. The next time you see a car, truck, or bus anywhere in Texas with dirty smoke coming from its exhaust for more than 10 consecutive seconds, write down the license number, date, time, and location you saw the smoking vehicle.
Report the smoking vehicle, within 30 days, by submitting the online reporting form in English, in Spanish or calling 1-800-453-SMOG (7664). You do not have to give your name, and the report is free.
The TCEQ will then notify the owner that his or her vehicle may be contributing to air pollution by smoking excessively. The TCEQ will also provide the owner with information about how car maintenance will improve the vehicle's performance.
Does this help? Yes! So far, more than 160,000 cars have voluntarily gone in for emissions repairs, making a huge difference in the quality of air.
more and online reporting form at:
http://www.tceq.state.tx.us/implementation/air/mobilesource/vetech/smokingvehicles.html