Method and apparatus for testing vehicle exhaust emissions

This invention provides a method and apparatus for testing exhaust emissions of vehicles having internal combustion engines. The apparatus of the present invention comprises a test track over which a vehicle is moved under its own power and remote exhaust testers which spectroscopically test exhaust emissions of vehicles as they move over the test track. The apparatus and method of the present invention preferably may be used for pre-screening vehicles as a first step in a testing process utilizing, as a second step, more extensive testing as with stationary testing apparatus. Those vehicles clearly meeting minimum emissions standards can be relatively quickly screened out by the method and apparatus of the present invention and exempted from further, more extensive testing.

FIELD OF THE INVENTION 
This invention relates to testing exhaust emissions of vehicles having 
internal combustion engines. 
BACKGROUND OF THE INVENTION 
Due to mounting concerns over air quality, numerous jurisdictions in North 
America, Europe and Asia have instituted mandatory testing programs 
wherein exhaust emissions of vehicles are tested to determine whether they 
meet minimum standards set by a government agency. Typically, this testing 
of exhaust emissions is conducted annually and is a necessary precondition 
to renewal of vehicle registration. United States government standards for 
volatile organic compounds, oxides of nitrogen and carbon monoxide as 
defined by the U.S. Environmental Protection Agency are contained in the 
Federal Register, Part 51. 
It has been found that most vehicles meet emissions standards. Most 
vehicle-related air pollution is caused by a relatively small proportion 
of vehicles, many of which have emission control systems which are 
malfunctioning or have been tampered with. 
Presently used tests to accurately determine emission levels and to 
diagnose problems with vehicle emission controls are time consuming. 
Typically, vehicles must be brought to a central testing facility, and 
tested on a stationary testing apparatus by direct sampling of the 
exhaust. 
The disadvantage exists that widespread testing of vehicles using 
stationary testing apparatus is very time consuming. This results in undue 
hardship for motorists, who must endure long lineups at testing 
facilities. 
Another disadvantage exists that stationary testing apparatus is very 
expensive, and therefore the cost of testing a vehicle on stationary 
apparatus is relatively high. 
There are also presently available remote sensing testing apparatus which 
quickly test exhaust emissions by spectroscopic methods, which may 
generally be defined as methods which detect the presence of a substance 
by measurement of the radiant energy absorbed or emitted by the substance 
in any of the wavelengths of the electromagnetic spectrum. For example, 
presently available remote sensing testing apparatus typically test 
exhaust emissions by the use of ultrasensitive infrared detection 
technology. Remote sensing testing apparatus utilizing ultrasensitive 
infrared detection technology typically operates by passing a chopped 
infrared beam through the exhaust plume of a vehicle in close proximity to 
the exhaust pipe of the vehicle. The absorption intensity of the beam is 
measured after it is passed through the exhaust plume and the levels of 
certain target compounds present in the exhaust emissions of the vehicle 
are then calculated. 
In conclusion, the disadvantage exists that accurate testing of vehicle 
emissions using stationary testing apparatus is time consuming and 
expensive. Although quicker and cheaper, remote sensing testing is 
typically less accurate than stationary testing in estimating levels of 
vehicle emissions. 
SUMMARY OF THE INVENTION 
The present invention at least partially overcomes these disadvantages by 
providing an apparatus and a method for testing vehicles which is 
substantially faster and cheaper than stationary testing apparatus, and 
provides substantially greater precision than roadside remote sensing 
testing apparatus. 
The apparatus of the present invention comprises a test track over which a 
vehicle is moved under its own power. The apparatus includes remote 
sensing exhaust testers positioned along the track to test the exhaust 
emissions of vehicles as they are driven along the track. The exhaust 
emissions of the vehicles are preferably tested under at least two 
different modes of operation to provide a reliable indication of exhaust 
emissions. 
The apparatus and method of the present invention preferably may be used 
for pre-screening vehicles as a first step in a testing process utilizing, 
as a second step, more extensive testing as with stationary testing 
apparatus. Those vehicles, typically comprising a significant portion of 
vehicles being pre-screened, which clearly meet minimum emission 
standards, can be relatively quickly screened out and exempted from 
further testing. The vehicles which do not clearly meet minimum emission 
standards are then subjected to more extensive testing, as for example, by 
being tested and diagnosed on a stationary testing apparatus. 
Therefore, the method and apparatus of the present invention can be used to 
eliminate the need for stationary testing of a significant portion of 
vehicles. By quickly and effectively identifying polluting vehicles, the 
present invention substantially increases the speed of vehicle emission 
testing without sacrificing accuracy in the measurement of emission 
levels. 
It is one object of the present invention to provide an improved apparatus 
and method for testing exhaust emissions of internal combustion vehicles. 
It is a further object of the present invention to provide a pre-screening 
system to quickly identify and separate vehicles which clearly meet 
emission standards from those which do not or may not. 
In one aspect, the present invention comprises a method of testing exhaust 
emissions of vehicles having internal combustion engines to estimate 
whether the emissions of any vehicle meet predetermined standards, 
comprising: moving each vehicle under its own power along a test track 
under controlled conditions of operation, the test track having an 
upwardly inclined portion, a horizontal portion and a downwardly inclined 
portion, the method comprising the steps of: moving the vehicle to ascend 
the upwardly inclined portion at a positive rate of acceleration and 
within a first range of velocities, and remotely testing the exhaust 
emissions of the vehicles by spectroscopic means as the vehicle ascends 
the upwardly inclined portion at a first test point on the upwardly 
inclined portion; moving the vehicle across the horizontal portion at a 
substantially constant velocity and within a second range of velocities, 
and remotely testing the exhaust emissions of the vehicle by spectroscopic 
means as the vehicle crosses the horizontal portion at a second test point 
on the horizontal portion; and moving the vehicle to descend the 
downwardly inclined portion at a negative rate of acceleration and within 
a third range of velocities, and remotely testing the exhaust emissions of 
the vehicle by spectroscopic means as the vehicle descends the downwardly 
inclined portion at a third test point on the downwardly inclined portion; 
comparing the test results from the first, second and third test points of 
one vehicle with results for vehicles which meet the predetermined 
standards, said steps being performed in any order. 
In another aspect, the present invention provides an apparatus for testing 
exhaust emissions of vehicles having internal combustion engines, 
comprising: a test track over which vehicles are moved under their own 
power under controlled conditions of operation, the test track having an 
upwardly inclined portion, a horizontal portion and a downwardly inclined 
portion; a first remote sensing tester for testing the exhaust emissions 
of the vehicles by spectroscopic means, the first tester located at a 
first test point on the upwardly inclined portion; a second remote sensing 
tester for testing the exhaust emissions of the vehicles by spectroscopic 
means, the second tester located at a second test point on the second 
horizontal portion; a third remote tester for testing the exhaust 
emissions of the vehicles by spectroscopic means, the third tester located 
at a third test point on the third inclined portion; and a processor for 
comparing the test results from the first, second and third test points of 
one vehicle with results for vehicles which meet the predetermined 
standards. 
Preferably, a stream of air is directed at the track by a blower located 
ahead of a test point, vehicles passing through the air stream before 
moving past the test point, the air stream clearing from the track exhaust 
emissions carried along the track by a vehicle as the vehicle passes 
through the air stream, the exhaust emissions tested at the test point 
substantially comprising only an exhaust plume emitted by the exhaust pipe 
of the vehicle between the air stream and the test point. 
More preferably, a stream of air is directed at the track ahead of each 
test point. 
Preferably, the remote testers comprise a source of infrared radiation and 
a detector of infrared radiation, the source emitting a beam of infrared 
radiation which passes through an exhaust plume of a vehicle and is 
subsequently detected by the receiver, the exhaust plume located at the 
test point and in close proximity to the exhaust pipe of a vehicle. 
In yet another aspect, the present invention provides a method of testing 
exhaust emissions of vehicles having internal combustion engines, 
comprising: a first pre-screening step, comprising testing vehicles 
according to the method and apparatus of the present invention described 
above to estimate whether the emissions of any vehicle meet predetermined 
standards; and a second step comprising testing exhaust emissions to 
accurately determine whether the emissions of any vehicle meet 
predetermined standards, the second step not being conducted for vehicles 
likely to have emissions meeting the predetermined standard, as estimated 
by the pre-screening step.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A first preferred testing apparatus according to the present invention is 
shown in FIG. 1. 
The preferred apparatus 10 is shown in FIG. 1 as comprising a test track 
12, three remote sensing exhaust testers 14, each comprising a source 16 
and a detector 18 located on opposite sides of track 12, and three blowers 
20. 
FIG. 1 illustrates the test track 12 as comprising three portions; a first, 
upwardly inclined portion 22, a second, flat, horizontal portion 24, and a 
third, downwardly inclined portion 26. 
Vehicle 28 is moved over track 12 under its own power, first ascending 
along first inclined portion 22, then moving horizontally along horizontal 
portion 24, and lastly descending along second inclined portion 26. 
Vehicle 28 is moved over track 12 under controlled conditions of 
acceleration and velocity. Preferably, vehicle 28 starts from a stop at 
the bottom of first inclined portion 22 and ascends along inclined portion 
22 at a constant, positive, rate of acceleration, moves across second 
horizontal portion 24 with constant velocity, and then descends along the 
third inclined portion 26 at a constant, negative rate of acceleration. 
The exhaust emissions of vehicle 28 are tested at three test points 30, 32 
and 34 located along the track 12. 
The test points 30, 32 and 34 are illustrated in FIG. 1 as planes through 
which vehicle 28 passes as it moves along test track 12. 
First test point 30 is located proximate the upper end of the first 
inclined portion 22. At the first test point 30, the vehicle 28 is 
preferably accelerating at a constant rate up inclined portion 22. 
The second test point 32 is located on the second horizontal portion 24, 
preferably about two thirds of the distance along portion 24. At the 
second test point 32 the vehicle 28 is preferably moving at constant 
velocity along central portion 24. 
The third test point 34 is located on the third inclined portion 26 
proximate its upper end. At the third test point 34, the exhaust emissions 
of vehicle 28 are tested as it descends along third inclined portion 26, 
preferably at a constant negative rate of acceleration. 
The inventor has determined that the testing of exhaust emissions at the 
preferred locations of test points 30, 32 and 34 along test track 12 
provides a good approximation of exhaust emissions of vehicle 28. 
FIG. 2 illustrates a preferred manner in which the exhaust emissions of 
vehicle 28 are tested at one test point along a test track 12. 
FIG. 2 illustrates vehicle 28 having a conventional exhaust pipe 36 located 
at the rear of and underneath vehicle 28. Exhaust pipe 36 forms the 
terminal end of an exhaust system (not shown) through which exhaust 
emissions produced by the internal combustion engine powering vehicle 28 
are released into the environment. 
The exhaust emissions are released from exhaust pipe 36 in the form of an 
exhaust plume 38, which is a cloud of exhaust matter extending rearwardly 
from exhaust pipe 36 and located above the surface of test track 12. 
Typically, the most dense area of exhaust plume 38 is about 8 inches in 
diameter and is centred about 14 to 16 inches above track 12, depending on 
the height of exhaust pipe 36. 
FIG. 2 illustrates the exhaust plume 38 being tested at test point 40, 
shown as a plane, by remote sensing exhaust tester 41. 
The exhaust plume 38 is preferably tested in close proximity to the end of 
exhaust pipe 36. Therefore, a sensor is preferably provided along track 12 
to sense the passing of vehicle 28 through test point 40 and trigger the 
exhaust tester 41 to test the exhaust plume 38 of vehicle 28 as the 
exhaust plume 38 passes through test point 40. The sensor for detecting 
the passing of vehicle 28 may preferably form an integral part of remote 
sensing tester 41. 
One particularly preferred sensor/trigger mechanism passes a beam across 
track 12 transverse to the direction of travel of vehicle 12 at test point 
40. When the front of vehicle 28 breaks the sensor's beam, the sensor 
recognizes that the vehicle 28 is passing in front of the sensor. After 
the rear of vehicle passes through the beam, the beam passes across the 
track 12 uninterrupted. The sensor then triggers the remote sensing tester 
to test the exhaust emissions of vehicle 28 proximate exhaust pipe 36. 
Preferably, there is a short time delay between the instant the vehicle 28 
finishes passing through the beam and the triggering of the remote sensing 
tester to allow plume 38, located rearwardly of vehicle 28, to move to 
test point 40. 
The remote sensing exhaust tester 41 comprises a source of electromagnetic 
radiation 16 and a detector 18 which detects electromagnetic radiation 
emitted by source 16. 
Electromagnetic radiation may be defined as radiant energy in the form of 
electromagnetic waves, or light. The various forms of electromagnetic 
radiation comprising the electromagnetic spectrum are characterized by 
their wavelengths, and include cosmic rays, gamma rays, x-rays, UV rays, 
visible light rays, infrared, microwave and radiofrequency rays. 
Preferably, the electromagnetic radiation emitted by source 16 and 
received by detector 18 comprises UV or infrared, more preferably infrared 
of one or more wavelengths. Although UV and infrared are preferred in the 
method and apparatus of the present invention, it is to be understood that 
electromagnetic radiation of other wavelengths may also be suitable. 
Most preferably, source 16 emits a beam 42 comprising infrared radiation of 
at least one wavelength, each wavelength interacting with a target 
compound present in the exhaust emissions of vehicle 28. 
The beam 42 of infrared radiation emitted by source 16 is directed 
transversely across track 12 in the plane of test point 40. 
FIG. 2 illustrates a particularly preferred tester 41 wherein the source 16 
and detector 18 are located on the same side of track 12. The beam passes 
from source 16, through exhaust plume 38, to a reflector 19 on the 
opposite side of track 12. Reflector 19 reflects the beam back to detector 
18, through exhaust plume 38. 
The path length travelled by the beam is preferably about 25 feet, which is 
preferably about twice the width of track 12. Therefore, the configuration 
of tester 41 shown in FIG. 2 is preferably used when it is desired to 
locate tester 41 directly alongside track 12. However, it is to be 
understood that locating source 16 and detector 18 on opposite sides of 
track 12, as shown in FIG. 1, may be equally suitable. 
The absorption intensity of the infrared radiation received by detector 18 
is compared with the intensity of the infrared radiation emitted by source 
16 to provide a measurement representative of the quantity of one or more 
target compounds in the exhaust plume 38 of vehicle 28. 
The beam 42 emitted by source 16 preferably passes through the centre of 
exhaust plume 38, and in close proximity to the end of exhaust pipe 36. 
For vehicles such as vehicle 28 shown in FIG. 2 having an exhaust pipe 36 
slightly above track 14, the height of beam 42 is preferably about 12 to 
about 20 inches above the level of track 12, more preferably about 14 to 
about 16 inches above track 12. 
The acceleration and velocity of vehicle 28 are preferably monitored as it 
passes over track 12 to determine whether the motion of vehicle 28 is 
within predetermined parameters of velocity and acceleration. One 
preferred monitoring device is a piezoelectric strip 43 attached to track 
12. The strip 43 can be used to determine the velocity of vehicle 28 by 
measuring the time taken for one tire to move over strip 43. The 
acceleration can be determined by measuring the relative velocities of one 
front tire and one rear tire of vehicle 12 over strip 43. 
Although FIGS. 1 and 2 show only one piezoelectric strip 43, it is to be 
understood that any number of strips 43 may be positioned along track 12, 
and that strips 43 may be positioned at any desired interval, for example 
every 5 feet. Although not shown in FIG. 5 for convenience, it is to be 
understood that strips 43 are also preferably positioned along track 50 of 
FIG. 5. 
The reliability of the test results is at least partially dependent on the 
quality of the exhaust plume 38 emitted by vehicle 28. Environmental 
factors such as wind and rain tend to disperse the plume 38, causing 
unreliable test results. Therefore, the test track 12 is preferably 
sheltered from wind and precipitation, preferably within a building or 
shelter. 
Water may also be brought onto test track 12 by the vehicles being tested. 
For example, water entrained in tire treads or ice and snow attached to 
the chassis of a vehicle may be deposited on track 12. This water wets 
track 12 and may be sprayed upwardly by the wheels of vehicles as they 
move over track 12 placing water into the path of the emitted beam 42 from 
the tester 41 and possibly affecting the test results. This problem can be 
reduced by shaping track 12 so that water deposited on track 12 drains to 
the centre of track 12 and away from the paths of vehicle wheels. 
Preferably, as shown in FIG. 2, track 12 has a slightly V-shaped 
transverse cross-section and is provided with drains 44 at its centre so 
that water collecting in the centre of track 12 can be drained away. 
The inventor has also found that exhaust fumes collect under vehicle 28 and 
are entrained by vehicle 28 as it moves along track 12. If these entrained 
exhaust fumes are present when vehicle 28 passes test point 40, less 
accurate test results will be obtained since the exhaust fumes entrained 
by vehicle 28 will mix with the exhaust plume 38 being tested at test 
point 40. The entrained exhaust fumes may contain exhaust emissions 
emitted under different conditions than at the test point 40 and which may 
not be generally representative of the exhaust emissions of vehicle 28 at 
test point 40. 
Therefore, as shown in FIG. 2, blowers 20 are preferably positioned 
proximate track 12 to blow an air curtain 45 onto track 12. The blower 20 
preferably blows air substantially vertically downward onto track 12 and 
also substantially transverse to track 12. Preferably, the air flow is 
directed slightly rearwardly relative to the direction of travel of a 
vehicle 28. The blower 20 is preferably positioned so that air curtain 45 
can "break" exhaust plume 38 shortly before vehicle 28 passes test point 
40. The inventor has found that directing air flow slightly rearwardly 
more efficiently breaks the plume as vehicle 28 moves past a blower 20. 
The distance between air curtain 45 and test point 40 must be carefully 
controlled so that the exhaust plume 38 has sufficient time to 
re-establish itself between air curtain 45 and test point 40. The 
preferred distance between air curtain 45 and test point 40 is dependent 
on the velocity and acceleration of vehicle 28. 
Thus, when vehicle 28 passes through test point 40, substantially the only 
exhaust present will be that released from exhaust pipe 36 in the form of 
exhaust plume 38, the exhaust plume 38 forming between air curtain 45 and 
test point 40. 
Preferably, a blower 20 is located along track 12 ahead of each test point 
on the test track 12. Although not shown in FIG. 1, a blower 20 is 
preferably located ahead of each test point 30, 32 and 34 in order to 
break the exhaust plume of vehicle 28, while being located a sufficient 
distance from the test point to allow the exhaust plume of vehicle 28 to 
reestablish itself for testing at each test point 30, 32 and 34. 
As shown in FIG. 2, blower 20 preferably comprises two vertical pipes 15 
and a horizontal pipe 17 each provided with a row of holes 21, the holes 
21 being directed downwardly toward track 12 by horizontal pipe 17 and 
transversely across track 12 by vertical pipes 15. A source of air (not 
shown) supplies pressurized air to blower 20. As shown in FIG. 2, blower 
20 may preferably be supported on legs 23. 
It is preferred that vehicle 28 be tested under at least two different 
modes of operation, defined by one or more of velocity, acceleration, 
engine speed and the ratio of air to hydrocarbon fuel being consumed. 
These factors have an impact on the composition of the exhaust emissions. 
The vehicle 28 preferably moves up first inclined portion 22 in a "loaded" 
mode. In loaded mode, the vehicle is preferably accelerating up inclined 
portion 22, more preferably at a constant rate. To achieve loaded mode, 
vehicle 28 is preferably stopped at the bottom of first inclined portion 
22 before beginning its ascent along inclined portion 22. In the loaded 
mode, because the accelerator pedal is depressed by the driver, the engine 
speed is moderately high, preferably about 2,000 rpm, and the air:fuel 
ratio is moderately enriched, preferably in the range of from about 
14.7:1, the stoichiometric ratio for ordinary gasolines, to about 13.5:1. 
It is to be understood that loaded mode differs from "enriched" mode, 
wherein the accelerator pedal is substantially fully depressed and the 
air:fuel ratio is enriched to below about 13.5:1. 
The vehicle 28 preferably moves across horizontal portion 24 in "cruise" 
mode, wherein vehicle 28 is moving with substantially constant velocity. 
In cruise mode, the accelerator pedal is partially depressed, preferably 
less than in loaded mode, and therefore the engine speed in cruise mode is 
less than that in loaded mode, preferably from about 800 rpm to about 1500 
rpm. The air:fuel ratio in cruise mode is leaner than that in loaded mode, 
preferably from about 14.0:1 to about 15.0:1. 
On second inclined portion 26, vehicle 28 is in "deceleration" mode, and is 
preferably decelerated by engine braking along at least a portion of 
second inclined portion 26. In deceleration mode, the acceleration pedal 
is not depressed, the engine speed is preferably less than that in cruise 
mode and the air:fuel ratio is preferably leaner than that in cruise mode. 
It is to be understood that the above engine speeds and air:fuel ratios are 
only rough estimates and that the engine speeds and air:fuel ratios 
discussed above would not be applicable to all vehicles. 
The test track 12 shown in FIG. 1 may have any suitable dimensions. The 
inclined portions 22 and 26 may have different dimensions and slopes, 
although they are shown in FIG. 1 as preferably having substantially the 
same dimensions. Preferably, an angle of incline I measured between 
reference plane G defined by the base of track 12 and the upper surface 46 
of first inclined portion 22 and between reference plane G and the upper 
surface 48 of second inclined portion 26 is from about 2.degree. to about 
10.degree.. Most preferably, the angle of incline I of the inclined 
portions 22 and 26 is about 6.degree.. 
The lengths of inclined portions 22 and 26, as measured along reference 
plane G, are respectively designated L1 and L3 in FIG. 1. 
Preferably, the length L1 of inclined portion 22 is long enough to attain 
loaded mode and the length L3 of the inclined portion 26 is long enough to 
attain deceleration mode. More preferably, L1 and L3 are from about 30 to 
about 100 feet. Most preferably, the lengths L1 and L3 are about 63 feet. 
The inclined portions 22 and 26 preferably have the same height H, which is 
defined as the maximum vertical rise of the inclined portions 22 and 26 
above reference plane G. Preferably, height H is from about 2 to about 8 
feet. Most preferably, height H is about 4 feet. 
The length L2 of the horizontal portion 24 is long enough for vehicle 28 to 
change from loaded mode to cruise mode. Length L2 is preferably from about 
40 to about 200 feet, more preferably about 89 feet. 
The preferred test track 12 illustrated by FIG. 1 is elevated above 
reference plane G. However, it is to be appreciated that test track 12 may 
have numerous configurations. Firstly, test track 12 may comprise one or 
more inclined portions, with the preferred number of inclined portions 
being two, as shown in FIG. 1, and the test track may comprise more than 
one flat, horizontal portion. Secondly, the test track 12 is not 
necessarily raised above ground level, but may also be partially or wholly 
situated at or below ground level. 
With reference to the preferred apparatus shown in FIG. 1, FIGS. 3 and 4 
are plots of velocity versus time and velocity versus distance, 
respectively, illustrating preferred conditions of velocity and 
acceleration under which vehicle 28 is driven over a particularly 
preferred test track 12, having angle I of 6.degree., H of 4 feet, L1 and 
L3 both 63 feet and L2 of 89 feet. 
FIGS. 3 and 4 show that the velocity of vehicle 28 in loaded mode 
preferably increases at a constant rate of 3 mph/sec (4.4 ft/sec.sup.2) as 
it is driven over upwardly inclined portion 22. At the upper end of 
inclined portion 22, vehicle 28 reaches a maximum velocity of 23.5 ft/sec, 
this velocity being reasonably constant as vehicle 28 passes over 
horizontal portion 24 in cruise mode. When the vehicle 28 reaches 
downwardly inclined portion 26, it is preferably decelerated at a constant 
rate of 3 mph/sec. 
The inventor has found that the first test point 30 is most preferably 
located at a distance of about 50 feet from the lower end of inclined 
portion 22, the second test point 32 is most preferably located about 72 
feet from the beginning of horizontal portion 24, and third test point 34 
is preferably located about 14 feet from the upper end of inclined portion 
26. Regarding third test point 34, the inventor has found that the vehicle 
28 is preferably tested after the vehicle has attained deceleration mode 
and after engine braking has begun. 
Remote sensing exhaust testers 14 and 41 such as those described above in 
reference to FIGS. 1 and 2 are commercially available. One particularly 
preferred remote sensing exhaust tester is the RES-100 unit of the Santa 
Barbara Research Center, a subsidiary of Hughes Aircraft Company, sold 
under the trade mark "SMOG DOG". Remote sensing exhaust testers typically 
operate by measuring selective absorption of infrared radiation by one or 
more of carbon monoxide, carbon dioxide, hydrocarbons, nitrogen oxides 
NO.sub.x, wherein X is 1/2 to 3, and oxygen, some or all of which may be 
present in exhaust of vehicles having internal combustion engines. 
The apparatus of the present invention is preferably initially calibrated 
so that it provides test results reasonably consistent with test results 
provided by means which are known to be accurate, such as stationary 
testing apparatus. 
The calibration process preferably comprises testing exhaust emissions of 
vehicles using the method of the invention, and comparing the test results 
obtained according to the present invention with test results obtained by 
other methods known to be accurate. A correlation is determined between 
the test results obtained according to the present invention and the 
exhaust emissions accurately determined by other methods. 
Using the correlation, it can be determined, with varying levels of 
probability, whether any vehicle tested according to the present invention 
will meet predetermined standard levels of emissions, for example as 
prescribed by a government agency. 
To improve the correlation between the test results according to the 
present invention and the levels of exhaust emissions accurately 
determined by other methods, the rate of acceleration and the velocity of 
each vehicle are preferably carefully controlled as the vehicle passes 
each test point along the test track. 
Therefore, it is most preferred that the vehicles be driven over the track 
by experienced test drivers capable of keeping velocity and acceleration 
within preset parameters. However, it is to be appreciated that the 
apparatus of the present invention can be calibrated to allow vehicle 
owners to drive their own vehicles over the test track. However, the test 
results would likely be more accurate when the vehicles are driven by 
skilled drivers. 
When used as a pre-screening step, the method of the present invention is 
preferably used to identify vehicles whose emissions with a very high 
level of certainty, meet standards more strict than the predetermined 
standard. 
For pre-screening, it is not necessary that the method of the present 
invention identify a high percentage of vehicles whose emissions meet the 
predetermined standard, only that at least some of these vehicles are 
identified and exempted from further, more extensive, testing. Reducing 
the number of vehicles subjected to extensive testing would attain at 
least one of the objects of the present invention. 
If the most preferred dimensions of the track 12 shown in FIG. 1 are used, 
with L1 and L3 equal to 63 feet and L2 equal to 89 feet, the total length 
of test track 12 will be 215 feet. Although the test track 12 is of a 
simple design, it would require a relatively large amount of space. 
FIG. 5 illustrates a second preferred test track 50 according to the 
present invention. Test track 50 is a four cornered loop having four 
straight sides, all sides having the same length. The preferred length of 
the sides is from about 20 to about 60 feet, with about 40 to about 50 
feet being most preferred. This track is preferable over that shown in 
FIG. 1 when space is limited. 
The first side 54 of track 50 is provided with an entrance ramp 56 and an 
exit ramp 58 by which vehicles (not shown) may enter and leave the test 
track 50, respectively. 
Second side 60 of track 50 has a downward inclined portion 62 of length L1. 
Downward incline 62 is preferably at an angle of about 5.degree. to about 
10.degree. to the horizontal, most preferably 6.degree., with length L1 
preferably being about 30 feet. 
The third side 66 of test track 50 is flat and horizontal. 
The fourth side 70 of test track 50 preferably has an upwardly inclined 
portion 72 of length L3. Preferably, the angle of incline 72 is from about 
5.degree. to about 10.degree. from the horizontal, most preferably 
6.degree.. Preferably, length L3 is about 20 to 30 feet. 
Preferably, a vehicle 28 (not shown) enters the first side 54 of test track 
50 via entrance ramp 56 and moves along test track 50 in the direction of 
the arrows in FIG. 5. Vehicle 28 is moved in deceleration mode, preferably 
at a constant negative rate of acceleration, over the downwardly inclined 
portion 62, with the exhaust emissions of vehicle 28 being tested at first 
test point 74 located at the lower end of inclined portion 62. 
The vehicle 28 preferably moves along the entire length of third side 66 in 
a cruise mode, preferably at a constant velocity. The exhaust emissions of 
vehicle 28 are tested as it moves past the second test point 76 located on 
the third side 66 of test track 50. 
On the fourth side 70 of test track 50, the vehicle is preferably 
accelerated in loaded mode at a constant rate of acceleration along 
upwardly inclined portion 72. The exhaust emissions of vehicle 28 are 
again tested at the third test point 78 located at the upper end of 
inclined portion 72. 
The vehicle 28 then proceeds along test track 50 back to the first side 54. 
The vehicle exhaust may preferably be tested at fourth test point 80 along 
first side 54, vehicle 28 moving in cruise mode, preferably at a constant 
velocity, past test point 80. The vehicle can then either leave test track 
50 by exit ramp 58, which adjoins first side 54, or may make another 
circuit of test track 50. 
At each of the test points 74, 76, 78 and 80 along test track 50 are 
located remote exhaust testers 14 comprising a source 16 and detector 18. 
These testers 14 are shown as being identical to those described above in 
reference to FIG. 1, however the source 16 and detector 18 may be on the 
same side of track 50 as shown in FIG. 2. 
Although not shown in FIG. 5, a blower 20 such as that shown in FIG. 2 is 
preferably positioned ahead of each test point 74, 76, 78 and 80 to break 
the exhaust plume with a curtain of air 45, a blower 20 being located a 
sufficient distance ahead of each test point to allow the exhaust plume to 
reestablish itself at the test point. 
As shown by FIG. 5, the three remote exhaust testers 16a, 16b and 16c are 
each connected by wires 82 to a main console 84. 
Console 84 is preferably provided with a processor (not shown) which 
processes the test results, correlates the results of individual tests, 
and compares the exhaust emissions determined by the tests with a 
predetermined standard. 
Each test result is preferably processed to determine firstly, whether or 
not instantaneous values of velocity and acceleration of a vehicle moving 
past a test point fall within predetermined ranges of velocity and 
acceleration; and secondly, whether or not average values of velocity and 
acceleration for movement of a vehicle over the entire test track, or any 
portion thereof, fall within predetermined ranges of velocity and 
acceleration. 
If the velocity and/or acceleration are not within the predetermined 
ranges, then one or more test results may preferably be discarded. On the 
other hand, if the velocity and/or acceleration are within predetermined 
ranges, then the processor preferably calculates the vehicle's exhaust 
emissions based on the instantaneous and average velocity and acceleration 
of the vehicle. 
Velocity and acceleration may preferably be measured by piezoelectric 
strips, such as strips 43 shown in FIG. 2, located at specified points 
along the test track, to determine the velocity and acceleration of the 
vehicle. Velocity may preferably be measured by determining the time 
required for one tire of the vehicle to pass over a strip 43, and 
acceleration may preferably be determined by measuring differences in 
velocity between a front and a rear tire of the vehicle. 
The processor preferably generates a profile of the velocity and 
acceleration of the vehicle as it moves over the test track. This profile 
shows whether or not movement of the vehicle is maintained within 
predetermined ranges for average velocity and acceleration over any 
portion of the test track, and whether or not the instantaneous velocity 
and acceleration of the vehicle at any test point is within predetermined 
ranges of instantaneous velocity and acceleration. 
The results of individual tests may individually be compared against the 
predetermined standard. Preferably, for the vehicle to pass the emissions 
test, at least two of the test results must meet the predetermined 
standard. 
Although the test results can be individually compared to the predetermined 
standard, it is more preferred that the test results be correlated to 
determine a composite level of emissions standards for the vehicle, this 
composite being compared against the predetermined standard. Preferably, a 
formula is utilized by the processor which combines test results obtained 
under different conditions of velocity and acceleration to obtain the 
composite emissions level for the vehicle. 
In one preferred embodiment, the composite emissions level is the average 
of the emissions levels determined at each test point. 
Although certain preferred methods for correlating test results and 
comparing them to a predetermined standard have been described above, it 
is to be appreciated that specific methods of correlating and comparing 
test results may be prescribed by government agencies in certain 
jurisdictions in which testing is carried out. Therefore, the processor 
may preferably be programmable so that it may be adapted for use in 
different jurisdictions requiring different methods of correlating and 
comparing test results. 
Although FIGS. 1 and 5 illustrate the test points being located at specific 
locations along test tracks 12 and 50, it is to be understood that the 
positioning of the test points is variable. 
Although test tracks 12 and 50 are shown as having inclined portions, it is 
to be appreciated that a test track according to the present invention 
could be designed which is substantially flat and horizontal throughout 
its entire length. Vehicles would be driven along such a track and tested 
at two or more test points under predetermined conditions of velocity and 
acceleration. The velocity and acceleration of the vehicle would be 
substantially entirely controlled by the vehicle driver. 
Although the invention has been described in connection with certain 
preferred embodiments, it is not intended that it be limited thereto. 
Rather, it is intended that the invention cover all alternate embodiments 
as may be within the scope of the following claims.