Remote Emissions Sensing                   Printer-friendly version

What Is It?

• Remote sensing technology uses infrared spectroscopy to identify high-emitting vehicles as they drive on highways. An infrared source emits a light beam across the highway, which passes through the emissions smoke before it arrives at a detector module. The difference in intensity between the received and emitted beams determines the ratio of CO/CO2 in the vehicle plume. If the level of carbon monoxide (CO) is above a certain threshold, a video system is used to record the license plate of the offending vehicle. See our Telecommunications Diagram on Emissions Sensing for more information.

• Remote sensing technology can be used as both an emissions control device and a research tool. Remote sensing could replace existing emissions control systems that require periodic mandatory vehicle inspections.

Key Results

So far initial tests of remote sensing technology in Los Angeles, Toronto, and Houston have been only moderately successful. The system is fairly accurate in identifying high CO emissions, but has had less success in detecting high levels of hydrocarbons (HC) and nitrogen oxides (NOX). In addition, tests of matching license plates to vehicle records have yielded inconclusive results. The entire remote sensing system still needs technological improvements before it can be used as an emissions control device. Potential Benefits

• Approximately 10% of the vehicle fleet causes 50% of all mobile CO, NOX, and HC emissions. Remote sensing technology allows identification of these super-emitters as they drive, eliminating opportunity for fraud, and perhaps leading to earlier correction of the problem

• Lower vehicle maintenance costs and emissions regulation compliance costs, since only offending vehicles would require inspection

• Can be used to evaluate emissions implications of traffic management strategies. The emission rates for CO and HC are related to the vehicle's instantaneous velocity and acceleration rate, which will be affected by traffic control and traffic management alternatives.

• Revenue generation through fines

Costs

• Further technological development of the system
  
• Infrastructure
• Administration costs such as ticket processing
• A remote sensing program is estimated to cost in the range of $18-60 million, while in Los Angeles, annual expenditures incurred under Smog Check, California's emission control program, total approximately $179 million per year.

Implementation Challenges

• Remote sensing is not as accurate as a stationary analyzer. While its detection of CO levels is near the accuracy of stationary analyzers, its detection of HC and NOX are much less accurate. In addition, perhaps its biggest disadvantage is that it only gives an instantaneous estimate of emission performance. It is well known that a vehicle's rate of emissions varies tremendously with acceleration and deceleration rates, cruising speed and engine temperature, as well as being inherently variable. Traditional stationary analyzers overcome this variation by testing the vehicle's emission rate over an extended period of time.

• Deployment would probably require new legislation at the state, and perhaps federal level for compliance with the 1991 Clean Air Act.

• Video Imaging must achieve a high enough level of accuracy for successful enforcement. A test of matching license plates to vehicle records in Toronto yielded a match rate of 95% (Steadman et al, 1992).

• Remote sensing technology will probably encounter institutional opposition from garage owners and others who currently perform smog checks.

Where is it implemented?

• US: New Mexico, North Carolina, Texas

• Europe: Budapest, Hungary

Author: Rebecca Pearson