Catch the culprit

  • 14/09/2000

The West has found several sophisticated ways to identify gross polluters. Two of them are remote sensing and on-board diagonistic systems.

Remote sensing
Remote sensing provides information about emissions without any equipment being connected to cars. A remote emissions sensor measures hydrocarbons (HC) and carbon monoxide (CO). The system operates by continuously projecting a beam of infrared radiation across a road and calculating the ratio of CO and HC to carbon dioxide before and after each vehicle passes by. By doing a comparison of the two readings the vehicles' emission rates of CO and HC can be determined. The equipment is combined with a freeze frame video camera to record the vehicles' license plate. Site selection is very important. A vehicle cruising at a constant speed on a level road has different instantaneous emissions rates than one accelerating up on an incline. However, as of now it is still not possible to measure nitrogen oxide levels. Besides, remote sensing is supposed to have a high error rate. It is also not capable of monitoring evaporative emissions. Several experts feel that the technology needs further development before it is taken up for wider application.

On-board diagnostic systems
OBD offers information about the car's emissions to the driver. OBD systems were started in the US from 1994 onwards and are expected to be introduced in the European Union for petrol vehicles this year and diesel vehicles from 2005. This is the only way a catalyst failure can be detected. However, it is possible that the OBD system itself can malfunction, be tampered with or simply be ignored. Hence, manual checks also become necessary.

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