Why does my laser alert go off under mway bridges?

[duncanreally]

It goes off almost as the car goes under the bridge, as if the laser is pointing straight down at the road. There are no camera vans or marks on the road.

Duncan

[Plotloss]

Trafficmaster?

Didnt think that was laser though.

[echo]

Plotloss said:

Trafficmaster? Didnt think that was laser though.

Traffic Master uses Infra-Red so could fall into the detection frequency range?

[puggit]

Yep - I've had the same problems and I've deducted it non-scientifically to be TrafficMaster.

[havoc]

I'd imagine so - AFAIK, most laser-"guns" are in the IR frequencies, so if you've a broad-band IR beam like trafficMaster, chances are it'll beep.

[trax]

If it was traffic master, I would have thought it would go off all the time though, as they are all over the place?? Sounds strange, unless it is the odd faulty traffic master thingy.

[havoc]

The blue poles are camera only, it's the dual-carriageway under-bridge thingy's that are IR.

[duncanreally]

Aah. Is there a solution? Maybe I can shield the detector (Valentine 1) so that is doesn't see the overhead Traffic Master IR source? Do you know if it is exactly the same wavelength (same diode) as the lasers used in speed traps?

Duncan

[regmolehusband]

The only place my laser detector goes off in that manner is beneath those ANPR jobbies on the bridge towards the top of the M40

"Reg"

[echo]

regmolehusband said:

The only place my laser detector goes off in that manner is beneath those ANPR jobbies on the bridge towards the top of the M40 "Reg"

Those cameras at the Warwick Jct. have IR floodlights to light up indexes in the dark IIRC.

[mel]

Is it attached to a RoadPilot by any chance ? If it is it's a known bug and my old one used to go off under bridges and from any strobe or flashing lights, if you phone them up they'll change it for a updated one FOC.

[Pigeon]

duncanreally said:

Aah. Is there a solution? Maybe I can shield the detector (Valentine 1) so that is doesn't see the overhead Traffic Master IR source? Do you know if it is exactly the same wavelength (same diode) as the lasers used in speed traps? Duncan

Semiconductor IR sources generally operate on one of two wavelengths which aren't very far apart anyway, in the region where photodetecting semiconductors are most sensitive, so probably not much good going this route.

Speed gun lasers are pulsed; it seems that if the Trafficmaster IR sources are setting off your detector they must be pulsed too (presumably LEDs with switched-mode current regulation). It may be possible to discriminate on frequency but that would require mods to the detector unit's software, so not too easy there either.