The FEAT is an instrument capable of remotely measuring tailpipe emissions from vehicles as they drive on the road. As such it is often referred to as a remote sensor. In 1987 with a grant from the Colorado Office of Energy Conservation the first successful FEAT was made and used to test light-duty vehicles in Colorado.

The FEAT was designed to emulate the results one would obtain using a conventional garage-type exhaust gas analyzer. An infrared and ultraviolet source are shined across a roadway onto multiple detectors which detect changes in the atmospheric concentrations of carbon dioxide (CO2), carbon monoxide (CO), unburned hydrocarbons (HC) and nitric oxide (NO) before and after the vehicle. A video picture of the back of the vehicle is simultaneously recorded. Because the effective plume path length and amount of plume seen depend on a number of factors the FEAT reports mass ratios of CO, HC, or NO to CO2 or gram of pollutant/kg or gallon of fuel consumed. Using these measured ratios as inputs to a standard combustion equation for gasoline many components of the vehicle operating characteristics can be determined including the instantaneous air/fuel ratio and the %CO, %HC, and %NO which would be read by a tailpipe probe.

The FEAT has been shown in double blind comparisons to be accurate to +/-5% for CO and +/-15% for HC. The NO channel is comparable to CO with a best case noise limit of 20 ppm, but has yet to be evaluated in a double
blind experiment. The video picture allows vehicle information from DMV to be correlated with the emission measurements.The FEAT completes the entire measurement process in less than a second and is
capable of measuring in excess of 2000 vehicles per hour at a busy location. It is primarily used in single lane environments but has been successfully used on two lane interstates. The car to the right was found in 1991 by the FEAT emitting 10.35% CO, 0.361% HC (3610 ppm) and 7.69% CO2. When stopped and inspected by California BAR

personel it was found to originally have been a diesel vehicle since converted to a gasoline engine with no emissions control equipment. Because it was still registered as a diesel vehicle it was not subject to California SmogCheck inspection program. The average vehicle at this location measured by the FEAT averaged 0.86% CO and 0.083% HC.

This system is currently the most cost effective method for obtaining a mobile source inventory for a city or region.

Review article links for additional information:

Measuring the Emissions of Passing Cars, D.H. Stedman and G.A. Bishop, Acc. Chem. Res., 29:489-495, 1996.

Spectroscopy Applied to On-Road Mobile Source Emissions, D.A. Burgard, G.A. Bishop, R.S. Stadtmuller, T.R. Dalton and D.H. Stedman, Appl. Spectrosc., 60:5:135A-148A, 2006.

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What's a FEAT? was last updated Monday, June 13, 2011