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From: (Bruce Hamilton)
Newsgroups: sci.environment
Subject: Re: Emissions Testing Questions
Date: Sat, 12 Aug 1995 18:52:04 GMT
Organization: Industrial Research Limited
Lines: 258

News is very delayed here, so apologies for  recycling another
thread, but Mary Bryant has also raised questions about 
remote sensing. I think that I have cut and pasted the FAQ info 
recently into another thread in sci.environment, so will I elaborate
a little more. The only way I can possibly relate this discussion
to current sci.environment threads is to suggest that it be used
to measure farts and burps from meat-eating mountain bikers
campaigning against mining to ascertain if they are nuclear or
fossil fuelled. :-)

In article <...> (Len Evens) writes:
>There is some evidence that the most effective way to reduce
>emissions from autos would be to monitor traffic with special
>equipment, stop the cars which are offenders and force them
>to repair their pollution control equipment (or in many cases
>stop disabling it).
>I'm afraid I don't have the reference handy, but this is based on
>a paper which appeared in Science in the past year I believe.

First, this technique has been around about 7 years, and I've been
posting details for about the last three. I even managed to convince
JdA in that it is a great idea before he departed last year.  I 
have based most of my contributions on papers from the University of 
Denver FEAT team, who are strongly for the technique, however the 
EPA have posted a very negative fact sheet on remote sensing at 

I do have a  very slight advantage over joe.public when evaluating
the claims, and that is that a team at IRL has built such a system
and are using it. They come and "borrow" my CO gas standard :-). 
So I'll include the relevent bit from the Gasoline FAQ and add some
more opinion ;-)

[ from Gasoline FAQ ]

5.14 What are "gross polluters"? 

It has always been known that the EPA emissions tests do not reflect real 
world conditions. There have been several attempts to identify vehicles on 
the road that do not comply with emissions standards. Recent remote sensing 
surveys have demonstrated that the highest 10% of CO emitters produce over 
50% of the pollution, and the same ratio applies for the HC emitters 
- which may not be the same vehicles [75-86]. 20% of the CO emitters are 
responsible for 80% of the CO emissions, consequently modifying gasoline 
composition is only one aspect of pollution reduction. The new additives can 
help maintain engine condition, but they can not compensate for out-of-tune,
worn, or tampered-with engines.

The most famous of these remote sensing systems is the FEAT ( Fuel Efficiency 
Automobile Test ) team from the University of Denver [78]. This team is 
probably the world leader in remote sensing of auto emissions to identify 
grossly polluting vehicles. The system measures CO/CO2 ratio, and the 
HC/CO2 ratio in the exhaust of vehicles passing through an infra-red light 
beam crossing the road 25cm above the surface. The system also includes a 
video system that records the licence plate, date, time, calculated exhaust 
CO, CO2, and HC. The system is effective for traffic lanes up to 18 metres
wide, however rain, snow, and water spray can cause scattering of the beam.
Reference signals monitor such effects and, if possible, compensate. The
system has been comprehensively validated, including using vehicles with 
on-board emissions monitoring instruments.

They can monitor up to 1000 vehicles an hour and, as an example,they were 
invited to Provo, Utah to monitor vehicles, and gross polluters would be 
offered free repairs [84]. They monitored over 10,000 vehicles and mailed 
114 letters to owners of vehicles newer than 1965 that had demonstrated high 
CO levels. They received 52 responses and repairs started in Dec. 1991, and 
continued to Mar 1992. They offered to purchase two vehicles at blue book 
price.  They were declined, and so attempted to modify those vehicles, even
though their condition did not justify the expense. 
 The entire monitored fleet at Provo (Utah) during Winter 1991/1992 
 Model year               Grams CO/gallon            Number of
                    (Median value) (mean value)      Vehicles
   92                    40             80              247
   91                    55                            1222
   90                    75                            1467
   89                    80                            1512
   88                    85                            1651
   87                    90                            1439
   86                   100            300             1563
   85                   120                            1575
   84                   125                            1206
   83                   145                             719
   82                   170                             639
   81                   230                             612
   80                   220            500              551
   79                   350                             667
   78                   420                             584
   77                   430                             430
   76                   770                             317
   75                   760            950              163
   Pre 75               920           1060              878

As observed elsewhere, over half the CO was emitted by about 10% of the 
vehicles. If the 47 worst polluting vehicles were removed, that achieves 
more than removing the 2,500 lowest emitting vehicles from the total tested 

Surveys of vehicle populations have demonstrated that emissions systems had 
been tampered with on over 40% of the gross polluters, and an additional 20% 
had defective emission control equipment [85]. No matter what changes are 
made to gasoline, if owners "tune" their engines for power, then the majority
of such "tuned" vehicle will become gross polluters. Professional repairs to 
gross polluters usually improves fuel consumption, resulting in a low cost to
owners ( $32/pa/Ton CO year ). The removal of CO in the Provo example above 
was costed at $200/Ton CO, compared to Inspection and Maintenance programs 
($780/Ton CO ), and oxygenates ( $1034-$1264/Ton CO in Colorado 1991-2 ), and
UNOCALs vehicle scrapping programme ( $1025/Ton of all pollutants ).

Thus, identifying and repairing or removing gross polluters can be far more 
cost-effective than playing around with reformulated gasolines and 
oxygenates. A recent study has confirmed that gross polluters are not always
older vehicles, and that vehicles have been scrapped that passed the 1993 new
vehicle emission standards [86]. The study also confirmed that if estimated
costs and benefits of various emission reduction strategies were applied to
the tested fleet, the identification and repair techniques are the most 
cost-effective means of reducing HC and CO. It should be noted that some 
strategies ( such as the use of oxygenates to replace aromatics and alkyl 
lead compounds ) have other environmental benefits. 

Action                      Vehicles   Estimated  % reduction  % reduction 
                            Affected     Cost                  per $billion
                           (millions) ($billion)   HC    CO     HC    CO
Reformulated Fuels            20         1.5       17    11     11     7.3
Scrap pre-1980 vehicles        3.2       2.2       33    42     15    19
Scrap pre-1988 vehicles       14.6      17         44    67      2.6   3.9
Repair worst 20% of vehicles   4         0.88      50    61     57     69
Repair worst 40% of vehicles   8         1.76      68    83     39     47


  75.  Emissions from 200,000 vehicles: a remote sensing study.
       P.L.Guenther, G.A.Bishop, J.E.Peterson, D.H.Stedman.
       Sci. Total Environ., v.146/147 p.297-302 (1994)

  76.  Remote Sensing of Vehicle Exhaust Emissions.
       S.H.Cadle and R.D.Stephens.
       Environ. Sci. Technol., v.28 p.258A-264A. (1994)

  77.  Real-World Vehicle Emissions: A Summary of the Third Annual CRC-APRAC
       On-Road Vehicle Emissions Workshop.
       S.H.Cadle, R.A.Gorse, D.R.Lawson.
       Air & Waste, v.43 p.1084-1090 (1993)
  78.  On-Road Emission Performance of Late-Model TWC-Cars as Measured by
       Remote Sensing
       Ake Sjodin
       Air & Waste, v.44 p.397-404 (1994)

  79.  Emission Characteristics of Mexico City Vehicles.
       S.P.Beaton, G.A.Bishop, and D.H.Stedman.
       J. Air Waste Manage. Assoc. v.42 p.1424-1429 (1992)

  80.  Enhancements of Remote Sensing for Vehicle Emissions in Tunnels.
       G.A.Bishop, D.H.Stedman and 12 others from GM, EPA etc.
       Air & Waste v.44 p.168-175 (1994)
  81.  The Cost of Reducing Emissions from Late-Model High-Emitting
       Vehicles Detected Via Remote Sensing.
       J. Air Waste Manage. Assoc. v.42 p.921-925 (1992)

  82.  On-road Vehicle Emissions: US studies.
       Sci.Total Environ. v.146/147 p.209-215 (1994)

  83.  IR Long-Path Photometry: A Remote Sensing Tool for Automobile 
       G.A.Bishop, J.R.Starkey, A.Ihlenfeldt, W.J.Williams, and D.H.Stedman.
       Analytical Chemistry, v.61 p.671A-677A (1989)

  84.  A Cost-Effectiveness Study of Carbon Monoxide Emissions Reduction
       Utilising Remote Sensing.
       G.A.Bishop, D.H.Stedman, J.E.Peterson, T.J.Hosick, and P.L.Guenther
       Air & Waste, v.42 p.978-985 (1993)

  85.  A presentation to the California I/M Review Committee of results of
       a 1991 pilot programme.
       D.R.Lawson, J.A.Gunderson
       29 January 1992.   

  86.  On-Road Vehicle Emissions: Regulations, Costs, and Benefits.
       S.P.Beaton, G.A.Bishop, Y.Zhang, L.L.Ashbaugh, D.R.Lawson, and
       Science, v.268 p.991-995. (1995)

[ End of FAQ stuff ]

The FAQ stuff is only based on what I have captured out of the 
scientific literature, and I'm loathe to put a reference to the EPA
site because they have not referenced their claims about the
fallibility of the technique. The technique is overhyped by Stedman
of the University of Denver, but that is probably partly a reaction to
the difficulty he has had getting officials to accept that remote
sensing can identify gross polutters. All the evidence I've seen
from our trials also indicates that it can generally identify vehicles
that are gross polluters. Certainly some of the EPA's criticisms
are justified, the technique is usually applied in areas ( such as
motorway off-ramps, or single lane streets ) and can not yet
handle multiple lanes, and will have some false hits and miss 
some, but given the small amount of funding, the number of
quality peer-reviewed research papers from Denver indicate
the potential direction of the technique.

The major advantage of the technique is that it actually identifies
the gross emitters without significantly penalising ( testing station
queues/costs etc. ) those who aren't grossly polluting. The technique
has  been extended to NOx, but there is far more work required on
that. Also as the emissions standards tighten, the HC content of
some air will exceed the exhaust emissions. Obviously it does not
measure evaporative and refuelling emissions, however such emissions 
are better addressed by playing with gasoline volatility and vehicle
fuel system design. 

Stedman also has a lot of patents on the technique, which may also 
motivate him, but I suspect a serious competitor could easily develop 
remote sensing techniques to successfully analyse NOx as well.
Note that several of their papers have covered correlations using
Testing Stations and the GM Instrumented car.  For the curious,
[83] provides the best technical description of the system, and [76]
provides a good current overview of the field. 

There are also several other papers that compare alternative
techniques for reducing vehicle emissions, many of which are
published as SAE papers, but it's highly likely that remote sensing
will further develop ( I'd like to see several beams across the road 
at differing heights to obtain a better profile and to ensure the
plume was trapped - but it is early days ), and the EPA will have
to consider it - especially if the US vehicle fleet age increases. 
Most of the limitations are due to atmospheric effects ( such as
rain etc. ) which can only be partially compensated for, as IR sources 
tend to be fairly low energy, and physical disruptions over the whole
path length do have an adverse effect.

If people wish to review some opinions on the subject, the following
are good introductions.

  61.  Achieving Acceptable Air Quality: Some Reflections on Controlling
       Vehicle Emissions.
       J.G.Calvert, J.B.Heywood, R.F.Sawyer, J.H.Seinfeld 
       Science v261 p37-45 (1993).

  69.  Improving Automobile Efficiency
       J.DeCicco, M.Ross
       Scientific American, December 1994. p.30-35.

  70.  Use market forces to reduce auto pollution.
       W.Harrington, M.A.Walls, V.McConnell.
       Chemtech, May 1995. p.55-60.

A good introduction to the whole field ( apart from the Gasoline FAQ -
which does discuss emissions in detail ) is the "Exhaust Control -
Automotive" monograph in the 9th volume of the  Kirk-Othmer Encyclopedia 
of Chemical Technology - 4th edition.   
                Bruce Hamilton

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