Remote Sensing           Identification
Process

Remote sensing units unobtrusively
measure exhaust emissions from
motor vehicles as they are driven
past on streets and highways.

Measurements are recorded in a
computer database without the
vehicle ever coming to a stop or
even slowing down. See below
for details.

Emissions are measured by casting a narrow infrared (IR) and ultraviolet (UV) beam of light across the road.

1 - The beam is projected across a single-lane roadway to avoid the interference that would occur from multiple exhaust plumes. A transfer mirror module then reflects IR/UV light back to a series of detectors that monitor light intensity at characteristic wavelengths. By measuring the absorption of IR/UV light by the various pollutants in the air, the system is able to calculate the pollutant concentrations in the vehicle exhaust plume.
2 - While emissions are measured, a video camera system captures an image of the vehicle’s license plate.
3 - Meanwhile, speed/acceleration sensors record the speed and acceleration of each vehicle.
4 - Emissions and related data are stored in a computer, monitored by an operator, in a van parked along the roadside.

The entire process is accomplished in a fraction of a second.