full paper - Insurance Institute for Highway Safety

Performance Under Controlled Conditions
of the Interceptor VG-2 Radar Detector
Detector
Adrian K. Lund
Scott Schmidt
Mark Freedman
Anthony C. Preuss
Michael A. Ciccone
June 1990
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FETY
ABSTRACT
The Interceptor VG-2 is a device developed to detect the use of radar detectors in moving
vehicles. In extensive off-highway tests, the Interceptor VG-2, or radar detector detector (ROD),
responded to all of 13 commercially available radar detectors. Although there was considerable
variation in the distance at which different radar detectors first evoked a response from the ROD, the
pattern of response was consistent across detectors: a gradually increasing intensity of response as
radar detectors approached the RODs, followed by an almost immediate cessation of response as the
radar detectors passed beyond the RODs. The response pattern was replicated for three different
vehicles (small plastic-body car, typical mid-size car, and large straight truck) and for different closing
speeds. The response of the RODs was also shown to be directional, so that radar detectors
approaching from the direction opposite the aim of the RODs produced only brief, much weaker
responses as they passed. The RODs were unaffected by the operation of radar speed-measuring
devices, and they were not detectable by approaching radar detectors. The RODs were subject to
interference from each other unless separated by at least 100 feet. There was also some interference
when a two-way radio microphone was activated within a couple of feet, but the interference was brief
and the pattern produced by the interference was unlike the response produced by passing radar
detectors.
Based on the off-highway testing, a protocol was developed for assessing radar detector use in
traffic and tested using three vehicles with radar detectors turned on or off according to a predetennined, random schedule. With the ROD, vehicles with operating radar detectors were positively
identified in 82 percent of the tests, and incorrectly identified as not having a detector only one
percent of the time. In 17 percent of the tests with an operating radar detector, a signal was recieved
but the signal could not be attributed positively to the test vehicle. Vehicles without operating
detectors were identified correctly as not having detectors in 61 percent of the tests and incorrectly as
having detectors in five percent of the tests. In the remaining 34 percent of tests without an operating
detector, a detennination about radar detector use in the test vehicle could not be made.
INTRODUCTION
Excessive speed is a major factor in crash losses. It contributes to both crash causation and to
the severity of crashes,l and enforcement of spee'd limits is an important element in an overall strategy
to reduce highway deaths and injuries. Police radar is one of the primary tools for enforcing speed
limit laws, but the proliferation of radar detectors, which are receivers that allow motorists to detect
police radar before their speed can be measured, diminishes its effectiveness?,3
To date, studies of radar detector use and enforcement of radar detector laws in the three
jurisdictions with these laws (Connecticut, Virginia, and Washington, D.C.) have been limited by the
lack of an easy method for determining radar detector use in moving vehicles. Most information about
radar detector use in traffic has been obtained from indirect measures, such as observed braking and/or
sudden speed reductions when passing vehicles are exposed to police radar.2,3
Direct observations of
radar detectors in vehicles have been reported,4 but these cover only visually obvious detectors and are
particularly suspect in jurisdictions that do not allow the use of radar detectors where they may be
concealed.
Clearly, both research and enforcement efforts would benefit from improved identification
of radar detector use. Recently, Technisonic Industries of Mississauga, Ontario has developed an
electronic device that offers a direct method for assessing radar detector use in moving vehicles.
All superheterodyne radar detectors use an internally generated microwave signal to enhance
their ability to detect police radar; this signal is broadcast by the radar detectors, and the Technisonic
Industries device, the Interceptor VG-2, is tuned to detect that characteristic signal. Thus, the
Interceptor VG-2 is designed to detect radar detectors in much the same manner as radar detectors
detect police radar. When the Interceptor VG-2 is near an operating radar detector, it responds with
both an audible tone and a visual display (a series of 10 light emitting diodes, or LEDs) that is
proportional to the microwave energy it receives from the detector. Figure 1 shows a photograph of
the actual unit and a diagram with a short explanation of the various controls and displays. Since
1988, the Ontario Provincial Police have been using this device to enforce an Ontario law banning the
use of radar detectors; during the first 30 hours of use in the London, Ontario area, they reported that
they confiscated 50 radar detectors. s
Ten of the Interceptor VG-2 devices, termed "radar detector detectors" (RODs), were obtained
for study. The purpose was to assess the sensitivity of the RODs, including their susceptibility to
interference from other possible sources of microwave radiation, and to assess their ability to
discriminate in actual traffic among vehicles known to have or not to have radar detectors. The first
This work was supported by the Insurance Institute for Highway Safety.
2
round of testing was conducted at an off-highway site where the sensitivity of the RDDs could be
tested under isolated conditions free of uncontrolled sources of microwave radiation. The on-highway
testing was conducted under controlled conditions on a stretch of rural interstate highway. This paper
reports the results of both sets of tests.
OFF-HIGHWAY TESTING
The purpose of the off-highway testing was to detennine whether the RDDs could detect a
wide variety of commercial radar detectors, at what range detection occurs, and whether there were
any performance differences under various ambient conditions and when installed in a variety of
vehicles. The testing was conducted at a nearly deserted airport near West Point, Virginia. The
airport was originally built for defense purposes during World War II with a total of 18,000 feet of
concrete runways. It is now used by small aircraft and is without tower control. This location was
selected because the ROD signal reception would not be influenced by stray signals from nearby
highways or other sources. The closest source of microwave radiation outside of CB and aircraft
communications was a remote VHF OMNI Range Radio (VOR) located 4.4 miles away.
RDD Sensitivity
The first objective of the off-highway tests was to detennine the sensitivity of the RDDs, or
their ability to detect the signals of commercially available radar detectors. These tests were
conducted using 13 popular radar detector models shown in Table 1. All 13 of these radar detectors
activated the RDDs at close range, as did three additional radar detectors that were purchased too late
for inclusion in this testing (Table 1).
The main series of sensitivity tests were performed on a 5,000-foot runway with an
observation vehicle, a large passenger van, stationed at the zero foot mark. A 4,000 foot range was
marked off in front of the van in 500-foot (or smaller) increments (Figure 2). As a target vehicle
approached the van with a radar detector in operation, notations were made of the response of the
RDDs at each incremental distance. For the first set of tests, the target vehicle was a small, plasticbody sports car (pontiac Fiero), and the radar detector was always mounted in the same location, near
the roof line (attached to the sunvisor or to the windshield) and aligned parallel to the longitudinal
center line of the target vehicle (Figure 3).
The 10 RDDs were mounted on a board fastened to the observation vehicle's instrument panel,
with the antennas aligned parallel to the longitudinal center line of the observation van (Figure 4).
3
The manufacturer recommends that the sensitivity dial of the RDD be set at the 2 o'clock position,
initially. Preliminary tests indicated, however, that this common setting left substantial variation in the
sensitivity of the RODs. To reduce this variation while assessing the characteristic response of RODs
to radar detector signals, the sensitivity settings were adjusted to produce a similar signal response on
all RDDs to one radar detector.· This was achieved by setting ROD #1 at the recommended 2
o'clock position and fmding the distance at which this radar detector was just detectable (3,500 feet).
Then, the sensitivity for each other RDD was adjusted to produce the same response at the same
distance. The resulting sensitivity settings for the 10 RODs ranged from 11 o'clock to 5:30 or nearly
maximum (see Table 2).
At the beginning of each test run, the radar detector was turned on and checked for operation
by directing police radar at it from the observation vehicle and confirming a response.
The van with
the ROD's was in a stationary position and the target vehicle approached the observation vehicle from
the opposite direction in the same lane. The target vehicle moved forward and stopped at each
distance increment, and the intensity of the signal response for each of the 10 RDDs was recorded.
Each RDD was tested one at a time because preliminary tests had indicated that interference occurred
whenever two were operated at the same time unless separated by at least 100 feet. The signal
intensity was measured by counting the number of light emitting diodes (LEDs) lit on the display of
the ROD, which ranged from zero to ten.
After all measurements at the 100-foot mark, the target vehicle then moved about 15 feet to its
driver's left and drove slowly past the observation van while ROD # 10 continued to monitor the
detector signal. Notations were made when the signal response reached zero.
Signal Response as Vehicle Approaches. All radar detectors were detected by all RDDs.
However, despite the initial sensitivity adjustments, there was still variability in the distance of
detection, both across RODs and across radar detectors. As shown in Table 2, the average distance at
which the tested RDDs first responded to an approaching radar detector was between 2,000 and 3,000
feet. Depending on the ROD, the distance at which a radar detector was first sensed varied from as
close as 100 feet to as far as the maximum test distance of 4,000 feet. In addition, some RODs
responded more strongly to some radar detectors than others.
•
The radar detector (A in Table 3) used for the sensitivity adjustments had been shown to emit somewhat greater than average
microwave radiation in bench tests of 11 radar detectors commercially available in 1988 (Insurance Institute for Highway Safety, unpublished
data).
4
However, these differences among the RDDs related primarily to the strength of the response
and how early the radar detector was itself detected. In using the RODs to identify vehicles using
radar detectors, the pattern of signal response is as important as the initial detection distance. Table 3
shows the pattern of response to radar detector A, whose pattern was typical of most other radar
detectors. As shown, the RDD response typically increased gradually as the vehicle was brought
closer to the RDDs. The major exception to this pattern occurred with RDD #3, which often
responded more weakly than other RODs and also had a less infonnative pattern of response. On two
of the 13 radar detectors, ROD #3 had a relatively flat response curve and, in a third case, a response
that appeared at one distance and then disappeared at a closer distance.
The relatively poorer perfonnance of RDD #3 is indicated clearly in another summary statistic
for the RDDs in this sensitivity test. An integrated signal intensity was computed for each ROD and
radar detector combination by multiplying the signal response at each test distance by the distance
between successive reading locations (in hundreds of feet) and summing the products (Table 4). An
average integrated signal intensity was then obtained for each RDD by averaging across the 13 radar
detectors. Most RDDs had an average signal intensity between 125 and 190. ROD #3 was much less
sensitive, achieving a score of only 55. The next weakest ROD was #5, which also had a score less
than 100. Although this indicates that RDD #5 was less sensitive, overall, than the other RODs, its
signal response still followed the typical pattern of increasing response as the radar detectors
approached the observation van; its response simply started at a closer point. The atypical
perfonnance of ROD #3 suggested that this RDD probably needed factory readjustment.
Signal Response as Vehicle Passes. The signal responses registered on RDD #10 declined
sharply as the vehicle passed the observation van. By the time the radar detector had passed 50 feet
beyond the ROD, the response had fallen to zero for every radar detector. In the majority of cases,
the response fell to zero as soon as the radar detector passed the RDD.
Velocity Effects
To detennine if relative motion between the radar detector and the RDD could affect the
performance of the RODs, the tests were repeated for one RDD and one radar detector, with the target
vehicle traveling at 10, 20, 30, and 40 mph. Speeds faster than 40 mph were not tested because that
was the maximum speed that still allowed sufficient time to read and record the LEDs on the ROD as
the target vehicle passed each 500-foot marker. The ROD gave virtually the same reading as the
5
stationary tests at each distance for all test speeds; most readings were identical, and a few differed by
one LED (Figure 5).
Vehicle Size and Construction Effects
Potential effects of vehicle size and construction on ROD perfonnance were assessed by
repeating the RDD sensitivity tests with two additional vehicles: a Toyota Camry four-door sedan, a
midsize car with typical steel unibody construction, and a large straight truck (GVWR = 22,940 lbs)
also with steel construction. These tests were conducted using two RODs and five radar detectors.
The RODs selected were #8, which had the highest average response intensity at 1,500 feet, and #7,
which had the third lowest average response intensity at 1,500 feet. The radar detectors were A, B, C,
D, and G, which represented both "noisy" and "quiet" radar detectors, in tenns of the responses they
produced from the RODs during the first sensitivity tests. The detectors were mounted near each
vehicles' roofline, as in the first tests with the Pontiac Fiero.
Overall, there were few differences in response patterns among the three vehicles; Figure 6
contains an example of the typical results. Results for the two RODs were very similar and their
signal responses were averaged. One exception to the typical pattern occurred with radar detector G,
which evoked a much weaker signal from RDD #7 and from both RDDs when used in the Toyota
Camry.
In the only other consistent difference among the vehicles, the signal response of the RDDs
declined even more sharply for the Camry and the truck as they veered past the observation van than
for the Fiero. As measured on RDD #8, the most sensitive of the RODs, the response to all five radar
detectors in these two vehicles had fallen to zero within 25 feet beyond the front of the van.
Opposing Vehicle Tests
Tests were also conducted to measure the response of the RODs to radar detectors approaching
from the opposite direction (i.e., approaching from behind the RDDs), simulating opposing vehicle
traffic on actual highways. Readings were taken with the ROD and radar detector antennas aimed in
the same direction along the longitudinal axes of the vehicles and with the ROD aimed 60 degrees off
the longitudinal axis, toward the travel lane of the target vehicles (see Figure 7). Several sets of
opposing vehicle tests were conducted using the smaller set of five radar detectors and two RODs,
using different target vehicles and simulating different lane offsets. The Toyota Camry and large truck
6
tests simulated a 50-foot median between approaching traffic and opposing traffic, while tests with the
Pontiac Fiero simulated both 100-foot and ISO-foot medians.
In all opposing vehicle tests, readings were taken starting from 200 feet to the rear of the
observation van and continuing to 500 feet beyond the front of the obsetvation van. Readings were
taken every 25 feet until the target vehicle passed the front of the van, after which readings were taken
every 100 feet.
RDD response to the radar detectors in opposing vehicles was typically much weaker than the
response to approaching vehicles regardless of the width of the simulated median, the type of vehicle,
or the angular orientation of the RDD (to 60 degrees). Figure 8 is an example of results from the
Fiero tests with a 100-foot median and the RDDs oriented along the axis of the van. It shows both the
approaching and opposing lane RDD signal response, illustrating both the weaker response and the
more erratic response to radar detectors in opposing vehicles. Even at offsets of only 50 feet, the
response to radar detectors in opposing vehicles was much weaker than for approaching vehicles and
lasted only for a short distance. Rotating the RDDs orientation 60 degrees toward the target vehicle's
travel lane increased the magnitude of the response only slightly, and the pattern of response was very
similar to the zero degree test (Figure 9 provides an example of large truck results). For the Fiero
simulating opposing traffic across a 150-fi median, there was no RDD indication of a radar detector
presence for most radar detectors and RDD test combinations.
Again, radar detector G provided an exception to these typical results. The weaker response
that it evoked from the RDDs in the approaching vehicle tests was only slightly stronger than the
response it evoked in the opposing traffic test.
Radar Detector Location Effects
In all preceding tests, the radar detectors were located near the roofline of the target vehicles.
To assess whether location of the detector within a vehicle would affect the perfonnance of the RODs,
additional tests were conducted with the truck as the target vehicle. At distances of 3,500, 500, and
200 ft, radar detector #D was moved around the truck cabin, while the responses of RDD #7 and 8
were monitored. The radar detector position was varied from the roofline to the dashboard and from
the driver side A-pillar to the passenger side A-pillar. There was no measurable difference found in
signal intensity, as measured by the number of LEDs lit on the RDDs.
7
Effect of Radar Speed Measurement Devices
Each of the 10 RODs was positioned within three feet of standard radar speed measurement
units that were either tuned to police radar frequencies (and therefore detectable by radar detectors) or
tuned to a slightly different frequency that has been used for research purposes because it is
undetectable by radar detectors.2 The antennas of the radar units and the RDDs were aimed directly at
each other. There was no response of the RODs to either radar speed measurement device.
Two-Way Radios
During test runs, it was noted that switching on the microphone of a CB radio or a FM twoway radio caused a brief response from the ROD, but this occurred only if the microphone was located
within two feet of the RDD.
Temperature
The sensitivity of the RDDs to ambient temperature was tested by creating an enclosure for
RDD #8 and ducting the obselVation vehicle's heat into the RDD's enclosure. A thennocouple was
used to record the environmental temperature. A maximum temperature of 1200 F was obtained and
held for 30 minutes with the outside ambient temperature at 650 F. The Toyota Camry was stationed
at 1,500 feet with a radar detector; the detector produced a 5-6 LED output from the single RDD at
ambient temperature in the heat chamber. During the heat-up and heat-soaking process the RDD
power switch remained on and a reading was taken every 5 minutes. The LED output of the ROD did
not change throughout the whole test sequence.
RDD Detection by Radar Detectors
At no time during the off-highway tests did any of the radar detectors respond to the RDDs.
Summary of RDD Off-Highway Tests
A1113 of the tested radar detectors produced measurable responses from all 10 RODs. In
most cases, these responses occurred as early as 1,500 feet, although some detectors produced no
response until closer to some RODs. More importantly, the RODs were highly directional, and there
was a definite typical pattern of response: Radar detectors approaching from the monitored direction
produce a gradually increasing signal response from the RODs that drops off sharply (within 50 feet)
as the monitored vehicle passes the RDD..Additionally, vehicles simulating opposing traffic with
8
radar detectors produce much weaker ROD response patterns that are more erratic and are detectable
for much shorter distances than vehicles traveling in the lane being monitored for detector use. The
somewhat atypical performance of RDD #3 suggests that the manufacturer may need to refine some of
the manufacturing tolerances, but, even this RDD could be expected to identify many operating radar
detectors with precision in passing vehicles.
There are two conditions that may reduce the certainty of identification of detector-equipped
vehicles. First, if traffic is dense, vehicles may be following very closely or even traveling side by
side. If there is less than one to two seconds between vehicles, it will be difficult to identify which
vehicle (perhaps both) is responsible for a positive RDD response, even if the characteristic signal
discussed above is very clear. Second if a vehicle with an operating detector is followed by another
vehicle also with an operating detector that emits a sufficiently large amount of microwave radiation,
the second detector may prevent the characteristic drop in ROD response that would normally occur as
the first vehicle passes. The off-highway tests indicate that some radar detectors evoke a strong
response from RDDs from as far away as 3,000 feet. Thus, without the characteristic drop in RDD
response as the vehicle passes, radar detector use by the first vehicle will not be completely certain.
ON-HIGHWAY TESTING
In the second phase of testing, controlled on-highway tests were conducted to determine the
reliability of the RDD in identifying whether a particular vehicle in the traffic stream contains an
operating radar detector. For these tests, a ROD operator and an assistant were in a large passenger
van parked in an open area beyond the right shoulder of a low-to-moderate traffic volume section of
westbound 1-70, near Hancock, Maryland. While they observed traffic in the westbound lanes, three
vehicles operated by other experimenters were introduced into the normal flow of traffic, sometimes
with an operating radar detector, sometimes not. The vehicles maintained a separation distance from
each other corresponding to about three minutes at 55 mph. The drivers told the RDD operator via
two-way radio when they were approaching, and they traveled with their headlights on to further
facilitate identification. However, the RDD operator and assistant were not infonned whether a radar
detector was operating or not.
The observation site was selected because the westbound lanes were separated from the
eastbound lanes by a wide median and higher elevation; thus, radar detector signals from eastbound
vehicles were mostly blocked from a RDD aimed toward approaching westbound traffic. In addition,
9
the location was on a long straightaway that followed a right-bending CUlVe around a mountainside,
which helped block most radar detector emissions from following vehicles far upstream in the
westbound lanes. To further shield the RDD from upstream radar detectors that might mask any
signals from the target vehicles, the RDD was aimed at an angle of 45 to 60 degrees from the
longitudinal axis of the obselVation vehicle toward approaching westbound traffic. The off-highway
testing had shown that this angle did not appreciably increase the response of the RDDs to radar
detectors in traffic from the opposite direction (which was already shielded by the median), and it
could be expected to decrease the response of the RDDs to upstream traffic because of the high
directionality of their sensitivity to radar detectors.
On-Highway Procedure
The three target vehicles were small cars with steel construction. Except for slightly greater
response to radar detectors in the plastic-bodied Fiero, the off-highway testing had indicated that
vehicle size and construction had little effect on RDD response. Each vehicle was equipped with two
radar detectors, one relatively quiet and one relatively noisy, as judged by the off-highway testing.
The six devices included radar detectors A, B, C, I, and L from the off-highway testing, plus the
Cincinnati Microwave Solo detector purchased subsequently; the latter was included as an example of
the most recent technology in radar detector devices.
As the target vehicles approached the obselVation point, the drivers turned the detectors on or
off according to a pre-determined, randomized schedule. Each target vehicle drove past the
observation van 40 times on each of the two days, for a total of 240 trails. Half the trials were with
both radar detectors off; half were with one or the other detector on.··
As each target vehicle approached, it was obselVed through the left rear door window of the
van. RDD #8, which was mounted on a tripod, was used in the on-highway tests. After each target
vehicle passed by, the RDD operator answered the following questions about the trial:
1.
Did the RDD respond as the target vehicle passed? The answer was affirmative if any
LEDs lit on the RDD during the [mal 500 feet of the target's approach.
.... At the end of testing it· was noted by one driver that he had accidentally presented one trial with the radar detector on when it should have
been off; therefore, there were 121 trials with a radar detector on and 119 without.
10
2.
Was the operator certain that a radar detector signal had activated the RDD? If the
RDD responded as the target approached and the response was characteristic of radar
detectors and not erratic, the answer was affirmative.
3.
If the operator was certain a radar detector signal had been received, was the operator
certain that the target vehicle was responsible for it? This was answered affirmatively
orl1y if the characteristic response identified in the off-highway testing occurred,
including the decline in RDD response as the target vehicle passed, and if there were
no other vehicles close enough to also account for the response. Consistent with the
off-highway results, the operator typically required at least 1-2 seconds (100-150 feet)
between the target vehicle and other vehicles before answering affinnatively.
4.
Was the target vehicle at least 2 seconds behind the nearest vehicle (short or long
headway)?
5.
Was the nearest following vehicle at least 5 seconds behind the target vehicle (short or
long tailway)?
Based on the results of the off-highway testing, a radar detector was to be attributed to a target
vehicle only if the answer to questions 1 through 3 were all "yes." If no RDD response occurred
while a target vehicle was in the specified range, then the target vehicle was identified as not having
an operating radar detector. If a characteristic response pattern was observed but it could not be
attributed to the target vehicle because of nearby traffic, the identification was listed as uncertain. The
identification was also listed as uncertain when an RDD response occurred but did not follow the
characteristic response pattern of declining sharply as the target vehicle passed beyond the van; in all
such cases, the signal pattern subsequently declined as a nearby following vehicle passed beyond the
van. As noted in the off-highway testing, the radar detector in the following vehicle could have
masked the expected decline in signal from an operating detector in the target vehicle, making it
difficult to determine whether the detector was operating in the target vehicle.
The ROD operator answered the first three questions and determined radar detector use with
no help from the assistant. The assistant recorded all data and helped with the headway and tailway
assessments. The latter were included in the study because previous studies in which speeds were
measured by nondetectable radar had found that headways and tailways of these magnitudes were
generally necessary to obtain valid measures of speed (note that the tailway requirement is larger than
the headway requirement because these studies usually measured speeds after vehicles had passed by
11
rather than as they approached).6 Because studies of radar detector use in real traffic will undoubtedly
include measures of vehicle speeds, one objective of the on-highway testing was to detennine the
perfonnance of the RDDs under the specific conditions when speed measures are likely to be
available. The headway and tailway assessments were included to address this question but were also
expected to provide some insight into the occurrence of uncertainty because of traffic density.
On-Highway Test Results
A summary of the radar detector identifications for the two days combined is shown in Table
5. Of the 119 trials with both radar detectors off, 73 (61 percent) were correctly identified as having
no radar detector on (i.e., the operator was certain that there had been no radar detector signal or that
any signal received had come from a source other than the target vehicle). In only six trials (5
percent), did the operator incorrectly identify a radar detector as operating when it was not. However,
on 40 (34 percent) of the off trials, the operator received a radar signal but could not localize it to the
test vehicle; thus, radar detector use was uncertain for the test vehicle.
Of the 121 trials with one or the other of the detectors in use, the operator correctly identified
the test vehicle as having an operating detector in 99 cases (82 percent); in only one case (1 percent)
did the RDD operator definitely not identify a test vehicle with an operating radar detector. In 21
cases (17 percent) with an operating radar detector, however, the operator received a signal but could
not localize it to the target vehicle.
Altogether, there were seven trials (3 percent) with definite identification errors, and 61 trials
(25 percent) with radar detector signals that could not be attributed to the test vehicles. The data were
examined by observation day and by headway and tailway (Table 6). Five of the six trials where the
ROD operator incorrectly identified a test vehicle as operating a radar detector occurred on the first
day of testing, with only one error on the second day. After viewing the first day's results, the
operator indicated that he had indeed assigned radar detectors to a few vehicles for which there was
some doubt; that is, although some signals seemed very likely to have come from the test vehicles,
there had been other vehicles that might have caused the ROO signal in certain circumstances. For the
second day, the operator altered his approach and assigned active radar detectors only to vehicles for
which he was absolutely certain of identifying radar detector use. Although the numbers of trials are
too few for the results to be statistically significant, there was an apparent increase on day 2 in the
number of trials where radar detector use was uncertain for the test vehicle (29 percent versus 22
12
percent on day 1); but the number of trials in which vehicles without a detector were incorrectly
identified as having one declined from 8 percent (5 of 60) to 2 percent (1 of 59).
There is no evidence that identification errors (3 percent of trials) were related to traffic
density, as five of the seven errors occurred during trials when both headways and tailways should
have been adequate for detennining radar detector use. However, identification uncertainty was
affected by short tailways (less than 5 seconds between the target vehicle and a following vehicle);
three out of every four trials with short tailways, either alone or in combination with short headways,
resulted in an uncertain identification of radar detector use by the test vehicle. By comparison, when
neither headways nor tailways were short, 88 percent of the trials resulted in certain identification.
Short headways (fewer than two seconds between the target vehicle and the vehicle in front of it)
seemed to pose less difficulty than short tailways, as 83 percent of such trials resulted in a definite
identification and no errors.
One reason for the greater uncertainty with close-following vehicles is that radar detectors in
those vehicles would mask any radar detector signal from the target vehicle, as discussed earlier, while
radar detectors in preceding vehicles pose a problem only when headways are very short (about 1
second or less).
However, it is urillkely that the presence of other radar detectors in the following
traffic is a complete explanation of the uncertainty associated with short tailways. It may be that, for
unknown reasons, short tailways were more likely than short headways to be very short (less than 1
second). However, the current study did not code headways and tailways with sufficient detail to
assess this possibility.
One clear finding was that more trials resulted in uncertain identification when the radar
detectors were off than when they were on (Chi-square
= 7.53, P < 0.05).
This is not surprising
because, when it is on, an approaching radar detector usually evokes a very distinctive pattern of
response from the RDD, as observed in the off-highway testing. This distinctive pattern can
sometimes even override competing signals from other sources, especially if the detector in the target
vehicle is relatively noisy and the other detectors are not very close (Le., more than 5 seconds behind
the target vehicle).
This shows clearly that a detector is operating in the target vehicle. However,
when no radar detector is operating in a target vehicle, a strong radar detector signal from a following
vehicle will produce a response from the RDD while the target vehicle is within the usual range for
identification. This situation, where the target has no radar detector, cannot be distinguished from the
masking situation where the signal from a relatively quiet detector in the target vehicle is masked by
13
the following vehicle's detector signal. Thus, it is more difficult to ascertain that a radar detector· is
off than if one is on.
To detennine if the errors or uncertainty tended to be associated with the amount of
microwave radiation transmitted by the radar detectors, the results for each detector were examined.
One of the quieter detectors was somewhat more difficult to identify, but a majority (60 percent) of
the on trials with that detector were still correctly identified by the ROD operator. Of the remaining
five detectors, one was positively identified in 75 percent of its on trials, three were detected in 85
percent of their on trials, and one was detected during all of its on trials.
DISCUSSION
The results of both the on-highway and off-highway testing indicate that the Interceptor VG-2
model RDD can be used to identify vehicles traveling with operating radar detectors. Using the
criteria outlined at the end of the off-highway testing to identify radar detector use, it is clear that a
number of vehicles with operating detectors may be missed because the detector signal cannot be
assigned to them with certainty (17 percent in the on-highway study), but using these procedures
results in very few identification errors (3 percent over both test days). On the second day of onhighway testing, a vehicle without an active detector was incorrectly identified only once in 59 trials;
similarly, a vehicle with an active detector was incorrectly identified as not having one only once in
61 trials.
Although these error rates were obtained under relatively favorable traffic conditions, it is
expected that more congested traffic would not increase identification errors because the errors were
not associated with the headway and tailway measures. However, more congested traffic would
increase the number of uncertain identifications.
When identification of radar detector use was restricted to trials that met the criteria for
obtaining vehicle speeds by radar measurement (2 seconds headway, 5 seconds tailway), only 12
percent of the identifications were not certain in the on-highway tests. When only the second day's
test results are considered, this percentage increased slightly to 19 percent, but only two identification
errors were made in 120 trials.
All detectors tested were usually identifiable in the traffic stream when they were operating.
Even the latest technology detectors produced predictable responses in the RODs, and it is clear that
very little incorrect identification of radar detector use in a vehicle will be made if the criteria outlined
14
above are followed. Although there will be a substantial number of cases where the RDD will not be
able to assign a radar detector to a particular vehicle with certainty, that will usually occur because
there is another following vehicle with a radar detector that will be identifiable.
The results of these carefully controlled tests demonstrate that RDDs can be used to collect
useful data on radar detector use in vehicles in traffic. Most importantly, the fact that false positive
identifications are rare means that the device can be a useful tool to enforce radar detector bans.
References
1.
Solomon, D. 1964. Accidents on Main Rural Highways Related to Speed, Driver, and Vehicle. Washington,
D.C.: U.S. Dept. of Conunerce, Bureau of Public Roads.
2.
Ciccone, Michael A.; Goodson, Mark; and Pol1ner, Jessica. 1987. Radar Detectors and Speeds in Maryland
and Virginia. Journal of Police Science and Administration, 15:277-84.
3.
Pezoldt, V.l and Brackett, R.Q. 1988. The Impact of Radar Detectors on Highway Traffic Safety. College
Station, TX: Texas Transportation Institute, Texas A & M University.
4.
Maryland State Police. 1986. Prohibiting the manufacture, sale, use, and possession of radar detectors.
Anapolis, MD: Maryland State Police Traffic Program Planning Unit.
5.
The Ontario Provincial Police Review. 1989 Speeding target of new device. 24:(3)3.
6.
Freedman, Mark, and Esterlitz, Joy. 1990. The effect of the 65 mph speed limit on speeds in three states.
Transportation Research Board, in press.
605.SLF
15
Table 1
Radar Detectors Used In Off-Highway Testing
Make
Model
Serial #
Bel
Vector 3
F143898
Cincinnati Microwave
Escort
1264448
Cincinnati Microwave
Passport
803173
Cobra
Trapshooter
144726
Cobra
Trapshooter Ultra
229723
Craig
R101
16315052
ElectroIert
Fuzzbuster
M305082
K40
XK Superhet
546627
Maxon
RD 2A
0081241
Maxon
RD25
0024474
Uniden
RD 25
95047489
Whistler
Spectrum 2
191986
Whistler
Spectrum 2 SE
040895
*Cincinnati Microwave
Escort (new model)
E0048576
*Cincinnati Microwave Solo (new model)
S0036236
*Fox
V009404
Vixen III
* Models were purchased too late for 'field testing.
16
Table 2
Sensitivity of Radar Detector Detectors (RODs)
Sensitivity
Setting
Distance of First Detection (It)
(clock
position)
Average
1
2:00
2
RDD#
Shortest
Longest
2,804
100
3,500
2:00
2,604
500
3,500
3
5:30
2,257
1,500
4,000
4
11 :30
2,758
1,000
4,000
5
5:00
2,542
200
3,500
6
2:30
2,796
1,000
4,000
7
2:30
2,412
500
3,500
8
11 :00
2,912
1,000
4,000
9
2:00
2,335
500
3,500
10
4:00
2,642
1,000
3,500
17
Table 3
ROD Response as a Function of Distance For a Radar Detector #A
Signal Intensity (O-10) LEOS at Each Range (Ft.)
ROD #
4,000 3,500 3,000 2,500 2,000 1,500 1,000
500
200
100
8
0
1
5
7
8
9
10
10
10
10
6
0
1
5
7
8
9
9
9
10
10
7
0
1
5
7
8
9
9
9
10
10
4
0
1
5
7
8
9
9
9
10
10
2
0
1
5
7
8
9
9
9
10
10
1
0
1
5
7
8
9
9
9
10
10
9
0
1
3
7
8
8
9
9
9
9
10
0
1
3
7
7
8
8
9
9
9
5
0
1
3
7
7
7
8
9
9
9
3
0
1
3
3
5
5
5
5
5
5
18
Table 4
Integrated Signal Strength
RDD#
Radar
Detector
1
2
3
4
5
6
7
8
A·
242
242
135
242
210
242
242
B
46
54
15
40
6
46
C
8
12
21
27
37
D
157
175
50
187
E
217
230
92
F
192
207
G
109
H
9
10
250
225
215
32
68
29
22
48
104
36
102
21
81
167
107
195
96
97
255
127
217
129
260
142
182
38
205
92
190
150
222
127
132
115
74
135
82
137
103
186
103
132
235
206
51
230
97
170
82
220
152
135
I
152
147
54
165
89
160
71
190
92
135
K
132
132
26
125
60
125
104
157
112
95
L
225
220
76
255
132
240
175
290
167
192
N
245
250
68
285
147
250
185
300
177
192
P
112
175
23
107
70
118
195
87
175
120
Average
148
166
55
173
94
162
129
189
130
128
* Results for radar detectors are presented anonymously.
19
Table 5
Radar Detector Identifications In On-Highway Tests
On
Off
No.
0/0
No.
Total
%
No.
0/0
Actual Radar
Detector Status
119
(100)
121
(100)
240
(100)
RDD Identification
Correct
Incorrect
Uncertain
73
6
40
(61)
99
1
21
(82)
(1)
(17)
172
7
61
(72)
(3)
(25)
(5)
(34)
20
Table 6
Identifica'Uon of Radar Detector Use
By Observation Day and HeadwaylTailway Distance
Day 1
ROD
Short
Identification Headway
Alone
Short
Tallway Both
Alone
Short
Day 2
Neither
Short
Total
Short
Headway
Alone
Short
Tallway
Alone
Both
Short
Neither
Short Total
Off Trials
Uncertain
4
9
3
17
0
5
5
13
23
On (Incorrect) 0
1
0
4
5
0
0
0
1
1
Off (Correct)
2
2
3
31
38
3
0
0
32
35
Total
3
7
12
38
60
3
5
5
46
59
On Trials
Uncertain
0
8
0
9
2
3
3
4
12
On (Correct)
5
3
42
51
5
1
1
41
48
0
1
45
61
Off (Incorrect) 0
0
0
0
0
0
0
Total
2
11
42
60
7
4
5
5
FIGURE 2
Track Layout for ROD Approaching Vehicle Tests
4000 ft. - - - - - - - - . - - -
3500 ft. - - -
Radar Detector
Orientation
3000 ft. ---------..-
2500 ft. ---------..-
2000 ft.
-----1--
1500 ft.
----+--
Vehicle Path
1000 ft. - - - - - + - -
500 ft. - - - - - . - -
200 ft. - - - - + - 100 ft. - - - - - 1 . - - . . . . . ,
0--
ROD Orientation
I
Observing
Vehicle
15 ft.
FIGURE 5
Response of RDD #8 to Radar Detector D at Different Speeds
# of LEOs
10 , - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,
9t---------------tiM------------------------t
8r------iIQo-~IIB------~---------------------t
7r-------#----------.,;:~----------------I
6r--------I'-----------~----------------I
5t-------f------------~-------------I
4t-------f-------------~------------I
3r-------+---------------~-----------i
2r------t-----------------~~---------i
lr----t-------------------~--------t
OL-----tlII----...I..----....L.---"""'-------L-..---......I..---.......L--..---+--~-_+_
-500
0
500
1000
1500
2000
2500
3000
3500
Feet
I-
0 MPH
-I- 10 MPH
-4- 20 MPH
-e-- 30 MPH
-*- 40 MPH
4000
I
FIGURE 6
Average Response of RODs #7·8 to Radar Detector A by Target Vehicle
# of LEOs
10 ,...------*"........- = - + - - - - - - - - - - - - - - - - - - - - - - - - ,
9t'----+l--~~~-~~----*----------------t
8.....-----t-----------~~~~------+---------I
7.....----f----------------.;~~~---~------I
6f----f----------------~---Jl.p----~----I
5J---------t1------------------~~i-------~
4J-------ILo..----------J------------~~------I
3J------f-------------------~~-----I
2J------t---------------------~------I
11------+-------------------------.;~
O""-------;JJII~--'-----'------r.------'------r.----'---_--..
-500
0
500
1000
1500
2000
2500
3000
FEET
I
-
Fiero
-+- Truck
DATA REPRESENTS AN AVERAGE OF RDD #7-8
-4-
Camry
I
3500
4000
FIGURE 7
Track Layout for Opposing Vehicle Tests
- - - 500ft.
-------- 400 ft.
--+---
300 ft.
-------- 200 ft.
100 ft.
RDD
Orientation
o
----1--- -25 ft.
----f.--
r--
-50 ft.
----.-- -75 ft.
Observing
Vehicle
----1--- -100 ft.
----f.--
-125 ft.
----.---150 ft.
----1----175 ft.
----f.--
100 ft.
or
150 ft.
for Fiero
50 ft.
for truck,
Camry
-.~
ts1 RJ
R:DJ.
-200 ft.
Radar Detector
Orientation
~~"'"'-----Target Vehicle
FIGURE 8
Opposing Vehicle Tests - Average Response of RODs #7·8
To Radar Detector G in Pontiac Fiero at 100 Ft. Offset
Approaching Signal
Opposing Signal
500
1000
1500
2000
Feet
2500
3000
3500
4000
FIGURE 9
Opposing Vehicle Tests - Average Signal Response of RODs #7-8
To Radar Detector A in large Truck at 50 Ft. Offset
10
# of LED's
r-----I-----I~-------------------____,
Approaching Signal
9J------+--------:=j~----------------------l
81-------I---------------:~--+------i-----------l
7.....------1--------------~~---~------1
+
61----.f.-4-I.--------------------~----I
5~-~--t----------------------~-t
Opposing Signal RDD @ 60 Degrees
41----+N4~----+-----------------------1
3~--HHI-.....J.--4-------------------------I
Opposing Signal RDD@ 0 Degrees
21--~-4-I--J-----,t&.:....---------------------t
11-----I--+-.fI---+-\-~=------------------------t
O'-------&~I---~~~-----L------L.----'-----L-----&.---------L...------I
-500
o
500
1000
1500
2000
Feet
2500
3000
3500
4000