There was a report several years back of a radar unit reporting multiple consistently high readings, which were caused by reflection from a farmers windmill in the scanned area.
Radio/Microwave Interference can come in a variety of forms, both natural and man-made, but they have one thing in common - they produce a false or incorrect reading on the radar unit's display. Common sources of electromagnetic interference include airport radar; microwave transmissions; transmissions of CB, ham, VHF/UHF, and cellular two-way radio/ telephones, including police and business radios; faulty sparkplug wires; mercury vapor and neon lights; high-tension power-lines; and high voltage power substations. The radio energy from these sources can overload or confuse the sensitive circuits in a radar gun.
Obviously, radar beam reflection is an inherent ongoing problem that is still being experienced. Below are some of the regs regarding SA and VIC
Both sets of regulations state that the cameras should be set up on a straight section of road with no bends, and preferably no rise or fall or camber of road gradient.
SAPOL regs regarding cameras
To be used as a safety camera site a field assessment is undertaken by the Traffic
Camera Unit. Field assessments confirm the site:
is safe for the operator
is a straight section of roadway
does not have a pronounced super elevation (camber) that would distort an
incident image in the adjudication process
has a consistent speed limit
allows the operator to view vehicles approaching, passing through
and departing the radar beam
is clear of any reflective objects
is free of obstruction allowing sufficient distance in front of the radar to avoid
interference with the camera and radar operation, and the capture of a clear
camera image of the incident
is free of objects that would cause the radar beam to redirect
does not face directly into the sun.
Bends
Mobile safety cameras are only operated on a straight section of roadway.
Gradients
Mobile safety cameras may be operated on a slope, hill or gradient.
Redirection
Mobile safety cameras are radar units. Radar waves can redirect from certain
objects. Radar is highly susceptible to
redirection where there is a flat metal object or a
square vertically ridged metal surface.
In establishing mobile radar system care is taken to
ensure that there are no objects in or near the radar
beam that could cause redirection.
Redirection can be caused by:
Stobie poles
guard rails, either metal or concrete
flat metal signs
flat sided metal industrial bins
flat glassed areas (e.g. plate glass windows)
bus shelters
bridges
vehicles with large flat surfaces
(e.g. buses, semi - trailers)
metal fences with square vertically ridged
surfaces (note this does not include traditional
corrugated galvanised iron fences)
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Victoria Police Mobile Road Safety
Camera Policy & Operations Manual
© State of Victoria 2013
A site shall not
be:
a) On a bend in the road;
b) Within 200 metres of a change to a speed zone,
applicable to the same length of road, Exception
to (b) where a speed zone is defined by signs that;
Indicate a school zone or a school zone with declared school days; or
Contain additional information (e.g. times of operation),
Careful
background
evaluation of each site shall be
conducted for any sources of reflection
located in or near the radar beam position including;
a)
The possibility of vehicles entering or leaving
intersections, or travelling along service roads;
b)
Pole mounted electricity supply transformers;
c)
Mobile road safety camera
set-ups should not include sites where there are train lines which
are obscured by dense foliage – such that the
MRSCO is unable to determine whether a train
is present at the time a target vehicle is detected:
d)
Tram and train lines: Other than (c) above, the MRSCO must indicate on the Incident Log of
the Camera Operator’s Set-up notes the times that any images are taken where a tram or train
is within the area of the beam;
e)
Metal signs - house sale / auction signs and similar;
f)
Centre strip traffic signs such as No U Turn,
No Right / Left Turn, Keep Left, posted speed
limit signs and large advisory cross street signs;
g)
Armco road barriers or chevron signing;
h)
Metal bus stop shelters, public telephone
booths, Australia Post letterboxes;
i)
Sheet metal garage doors, fences, factory walls
and fencing structures which comprise of
closely spaced (10cm or less) vertical metal bars.
j)
Brick/Masonry Structures
These structures are divided into two parts;
Masonry structures that are over one metre in height and;
Very tall masonry structures such as factory walls.
Careful foreground evaluation shall also be conducted of
each site, to ensure that there are
no sources of reflection (e.g. traffic signs which
are larger than a street name, bus stop or
parking restriction sign):
Within 20 metres of the front of the camera vehicle when positioned against the kerb; or
Within 40 metres of the front of the camera vehicle/tripod when positioned off the road;
Within 50 metres of the front of the camera vehicle/tripod where very tall/large vehicles (or
similar sized reflective objects) are positioned in the foreground (this applies whether
positioned on or off road).
