A National Highways report into SVD (smart vehicle detection) trials published in 2016 stated that there were difficulties detecting small cars such as the Mazda MX5 sports coupe, which has a height of only 1.2 metres.
Hmm, if they are using radar to detect a vehicle, something with a lot of carbon or plastic has a low return signature, thus invisible.
There is a solution however, mount a âradar reflectorâ as fitted to smaller boats. One can be easily made with some kitchen foil!
For short range on the roads it will not need to be gigantic, (maybe 10cm square or less?) and could probably live inside the car if it has a plastic PRHT or a soft-top.
The Navtech system uses 77GHz, so quite small reflectors will work, as wavelength is 3.9mm.
I suppose you donât think of the MX-5 as a âstealthâ vehicle though in this context it is.
These so called Smart motorways have been dangerous from the the day they were opened.
There was a similar report that said - on average - 85 cars pass a broken down car BEFORE the system starts warning drivers to get out of the live lane.
There is a solution however, mount a âradar reflectorâ as fitted to smaller boats. One can be easily made with some kitchen foil!
Would a shiney chrome boot rack help reflect radar ? I am surrounded by the M25 and often use the so called smart M1, M4 or M3 before I get into the country. TIA
The clever point about the radar reflector mentioned is that itâs omnidirectional (unlike a looking glass mirror which has to be aimed). It reflects the full width (aperture) of a beam entering it straight back to the source, exactly like a cats-eye, with very little loss of âbrightnessâ.
The shiny boot rack is shiny because to scatters the pin-points of light in all directions, BUT all that scattering off the one tiny bit of curved surface actually mirroring back to the eye means we see only a fraction of what comes in.
A reflective road sign or a number plate has a layer of half-silvered glass beads. These do exactly the same as the radar reflector, but for visible light, and sadly are not useful for this radar as the beads are too small.
However, I was idly thinking if one could find something that looked like half-silvered bubble wrap with honeycomb-array style packing, and with decent hemispherical-silvered 1" bubbles, then if it was looking outwards and rolled around a standing baked bean tin it would work well enough.
The test is easy; shine a torch at it, if something on that scale reflects back even half as well as a cats eye itâll do the job.
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That will be me looking for an omnidirectional boot rack then, sure I must have a large baking tray somewhere in the house 
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