Even though the traffic in our major cities has increased enormously in the past 30 years, the overall pollution level is much lower than in the early 1970s, before the oxygen sensor and catalytic converter were installed in our cars.
New developments in catalytic converters oxygen sensors, and high-temperature ceramic particle filters (to filter out the smoke and soot from diesel engines) should further decrease pollution emissions from motor vehicles.
At the rate technology is progressing, these com bined ceramic systems might someday be so efficient that they could actually make the emissions coming out of our cars cleaner than the air entering our engines. What a dramatic change that would be we could use our cars to cleanse our air!