Living With Police Radar

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Police use hand-held or vehicle mounted radar units to monitor the
speed of vehicles for the purpose of traffic law enforcement. The units are
"low power" and have a range of only about one-half mile. The range
may be more or less depending upon terrain, weather, and the size of the
target vehicle.

Officers must usually be trained and certified to operate a radar unit
and to testify in court concerning readings obtained with it.

Traffic radar may be operated in the stationary mode or the moving
mode. Radar units are designed either for stationary use only, or may have a
switch to select stationary or moving operation. In the stationary mode the
officer parks the police vehicle at an advantageous location and directs the
radar antenna in the direction of the target vehicle. The target vehicle may
be either moving toward the radar unit or away from it. If the target is
large enough or close enough to reflect the radar signal back to the radar
unit, the target's speed will be recorded.

In the moving mode, the officer's vehicle must be in motion and can
monitor the speed of targets approaching from the opposite direction. The
radar unit measures the speed of the officer's vehicle and the speed of the
oncoming target vehicle. The two speeds are added to each other by the
radar's computer. Then the police vehicle speed is subtracted from the total
of the two thus giving the target speed. The readout is obtained in a
fraction of a second.

The radar unit must be calibrated at the beginning of each shift. Some
jurisdictions may require that the unit be calibrated before and after each
radar traffic stop is made. The unit may be calibrated manually and
electronically by the officer. Manual calibration is done by striking a small
tuning fork "cut" for a certain speed and holding the fork in front
of the radar antenna. If properly calibrated, the radar will indicate the
same speed as stamped on that particular tuning fork. The unit is also checked
by pressing a "calibrate" button on the radar and observing the
correct electronic responses indicating that the unit is functioning

Traffic radar is prone to a few errors if not operated by properly
trained personnel. Radar units operated inside the vehicle may read the speed
of the spinning ac/heater fan. This error is obvious because of the constant
"speed" readout in the absence of targets. The officer may
re-orient the antenna or turn off the fan while operating the radar. The
radar may read the speed of an unintended target due to the radar signal
being reflected off of large objects. Or the intended target may be a small
import car or motorcycle, and the speed actually obtained is the
"18-wheeler" further down the road. ( A larger portion of the
signal is returned from the "18-wheeler" even though it is farther
away.) These and other errors are easily avoided by the trained operator who
will choose a location favourable to radar operation and will reject
questionable readings when interfering targets or objects are present.



Good radar detectors will detect a signal
at a range greater than that at which the radar operator can get a reading.
The detector may be able to receive the radar signal a mile or more away, and
this range is too great for the radar signal to be reflected back to the
radar unit for a reading. Don't relax yet! Radar operators frequently leave
the unit in the "standby" mode when no traffic is present. When the
officers sees a vehicle which appears to be speeding, he can take the unit
off "standby" thus allowing it to transmit and "lock" on
to the target vehicle. If you're that first vehicle, your radar detector will
"beep", "flash" or whatever at the same time you're being
clocked. This will, however, let the "cat out of the bag" and alert
detector- equipped cars further down the road. Some operators don't care
about detector equipped cars and will leave the unit on continuously, knowing
that there are plenty of non detector-equipped speeding targets to be had.

Police Traffic Laser


Most new, high tech, items used by police agencies are never seen or
even heard of by the general public. This will not be the case with the new
traffic laser guns which began appearing several years ago.

These new handhold speed measuring devices utilise a narrow beam of
light, transmitted in pulses, that strike the target vehicle and then return
to the handhold unit where the speed is calculated.

The laser beam reportedly has a width of only three feet at a range of
1000 feet. This makes it easy to pick a single vehicle out of a pack and
obtain not only a speed readout but the exact distance to the target.

Radar detectors, which detect radio waves,
are useless against the new laser guns.

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