Remote gas analyzer for motor vehicle exhaust emissions surveillance

A method of determining pollutants in an exhaust plume of a motor vehicle moving along a road, comprising the steps of:

• passing a first array of gas analyzer beams along a first beam path through a predetermined space across said motor vehicle path so that said exhaust plume generated by said motor vehicle passes through said predetermined space, said first array of beams being positioned such that substantially an entire cross-sectional segment of said exhaust plume is intersected by said first array of beams along a predetermined length of said exhaust plume;
• measured the ambient amount of a first pollutant contained in said predetermined volume of space in a first measurement, and measuring the amount of said first pollutant in said predetermined volume after a motor vehicle exhaust has passed through said first array in a second measurement, said first and second measurements being performed by the use of said first array of beams;
• passing a second, multi-spectral gas analyzer beam along a second beam path adjacent said motor vehicle, said second beam path having sufficient length to allow a determination of the change in concentration of a plurality of pollutants from said exhaust plume intersecting beam second path relative to the concentration of said plurality of pollutants before said motor vehicle began to traverse said road, said plurality of pollutants including said first pollutant;
• measuring the ambient concentration of said plurality of pollutants in said exhaust plume intersecting said beam path of said second gas analyzer beam in a third measurement, said third measurement including the concentration of said first pollutant, and in a fourth measurement - measuring the concentration of said plurality of pollutants after said motor vehicle exhaust has passed through said second beam, said third and fourth measurements using said second gas analyzer beam;
• calculating a ratio by determining the relative increase in the amount of said first pollutant in the predetermined volume by use of said first and second measurements, and dividing that relative increase by the relative increase in the concentration of said first pollutant as determined from said third and fourth measurements;
• determining the relative increase in the amount per unit volume of said plurality of pollutants other than said first pollutant by using said ratio and said third and fourth concentration measurements for said plurality of gases.

A method of determining pollutants in an exhaust plume of a motor vehicle moving along a road, comprising the steps of:

• passing a first array of gas analyzer beams along a first beam path through a predetermined space across said motor vehicle path so that said exhaust plume generated by said motor vehicle passes through said predetermined space, said first array of beams being positioned such that substantially an entire cross-sectional segment of said exhaust plume is intersected by said first array of beams;
• measuring the increase in the amount of a first pollutant contained in a predetermined volume of space relative to the amount of said first pollutant after a motor vehicle exhaust has passed through said first array, using said first array of beams and further measuring the percentage increase of said first pollutant;
• passing a second, multi-spectral gas analyzer beam along a second beam path adjacent said motor vehicle, said second beam path having sufficient length to allow a determination of the change in concentration of a plurality of pollutants in said exhaust plume along said beam path relative to the concentration before said motor vehicle began to traverse said road, said plurality of pollutants including said first pollutant;
• measuring the change in concentration of said plurality of pollutants of said exhaust plume which intersect said beam path of said second gas analyzer beam, relative to the concentration when said motor vehicle began to traverse said road, using said second gas analyzer beam;
• determining the ratio of the relative increase determined from said first array, to the relative increase of said first pollutant from said second beam, and using that ratio with the relative change in concentration of said plurality of gases from said second gas analyzer beam to determine the relative increase in the amount per unit volume of said plurality of pollutants other than said first pollutant.