Speed camera question?

[StuartFZR400 0]

A duel carriageway has been reduced to a 50mph and two cameras placed on it.

 

Now when my old man bought a GPS, he just had to test it, and one of those tests was to check the accuracy of my speedo. We found it to be 1mph under all the way.

 

Knowing the accuracy of my speedo, Im confident to go through speed cameras on the dot. However on this above mentined road, I find the front facing camera seems to flash at me. Ive never seen one go off before, but this one certainly gives a glassy glint. And no its not the sun, and it has done it everyday. It doesnt do it when cars infront go through at about 46mph.

 

However this week it no longer does it, but i can see the glass lense inside. I dont want to test it at higher speeds to see if its thresh-hold has been lifted (if thats what you'd call it).

 

Anyone know why it was doing that?

Do cameras record people 'on the limit' ?

 

It stupidly amazing how many people drive at 60 - 70 on this road and slow down for the cameras - they're a waste of time !!!

[conleycrew3 0]

there's supposed to be a 10% margin on speed cameras, i dont know how well that is stuck to though

[Yandards 0]

there's supposed to be a 10% margin on speed cameras, i dont know how well that is stuck to though

 

Fairly confident it is at least 10% plus a figure as a minimum. As most speedo's are dependant on the outer circumferance of the tyre to give an accurate reading and you can start at around 8mm and drop down to 1.8mm (I think) then someone who is better at mathstthan me should be able to work out the difference in your speedo reading.

 

On top of that older cars use mechanical systems that have manufacturing tolerances that will give a range of readings depending on where in the tolerance range the one you have fitted is.

 

So to cut a long story short they have to give you an allowance to allow for the variables that are inherrent in the way a speedo works.

[dr_mat 0]

If it flashes at you it flashes twice.. Anything less is a coincidence - probably a reflection (particularly as you probably go past it at the same time every day and so on..)

The front-facing cameras don't flash, they tend to use the IR flash units for those (don't want to cause accidents by flashing in the eyes of the driver, now do they?).

[Musicman 0]

Fairly confident it is at least 10% plus a figure as a minimum. As most speedo's are dependant on the outer circumferance of the tyre to give an accurate reading and you can start at around 8mm and drop down to 1.8mm (I think) then someone who is better at mathstthan me should be able to work out the difference in your speedo reading.

 

worked example using your numbers

 

195/50/15 tyre:

 

RR = 288 mm -> circumference = 2PiR = 1809.6 mm

 

tyre wears down to 1.6 mm tread (the legal minimum)

 

RR = 281.6 mm -> circumference = 2PiR = 1769.3 mm

 

which makes for approx 2.2% difference in your speedo reading.

[Yandards 0]

Thanks MM, and that is just one part of the system and will not include the manufacturing tolerances on both the wheels and the tyres.

[StuartFZR400 0]

If it flashes at you it flashes twice.. Anything less is a coincidence - probably a reflection (particularly as you probably go past it at the same time every day and so on..)

The front-facing cameras don't flash, they tend to use the IR flash units for those (don't want to cause accidents by flashing in the eyes of the driver, now do they?).

You learn somthing every day - cheers. Like i say, its not a bright flash, nor is it just the light catching it; im sure; as the nature has changed this week and i no longer get it. I heard the rumour about 10% before and saw the logic to it, just sometimes you hear people getting done for 33 in a 30 - maybe they're fibbing.

[vr6storm 0]

the 10% IIRC is just a guideline............if you got a right t!t of a police force enforcing it they still can do you doing 33mph in a 30mph limit

[Musicman 0]

These are The Association of Chief Police Officers enforcement guideline figures

 

Limit	Fixed Penalty	Summons
20 mph		25 mph		35 mph
30 mph		35 mph		50 mph
40 mph		46 mph		66 mph
50 mph		57 mph		76 mph
60 mph		68 mph		86 mph
70 mph		79 mph		96 mph

 

As you can see, it works out that speeds in excess by 10% + 2mph of the posted limit will get you an FPN but, as has been previously noted, you could theoretically be pulled for being only 1 mph over the limit.

 

Click for the full document [MS Word Doc]

[exturbo2003 0]

just as a side note legally its the owners responsability to make sure ther speedo is accurate. a miss calibrated speedo is no defence. also usally speedos read fast as a safty margin

[NickRStorm 0]

Many GATSO type cameras will flash once as a warning that you are near to their trigger speed (I see this all the time in London on the A40 & North Circular) - it's when they flash twice that you need to worry! The front-facing cameras are the Truvelo type & work off strips in the road. As dr_mat says, they don't flash.

[BigTartanJudge 0]

Correct, GATSO's do indeed flash once if you are near to their trigger speed.

[G60Jet 1]

As Dr_Mat says Forward facing Camera dont have a flash, are you sure it was not monitoring the other side of the road

[StuartFZR400 0]

Duel carriageway, with central arm-co. Its defo speed-cam for my westbound direction. When I say "flash", its more of a glint. Suppose I'd need a photo to give you an example.

[bcstudent 0]

It's all in your head, I'm sure. Forward-facing cameras can't do anything that may be seen as distracting.

[Petros 0]

I've seen SPECS cameras (the avg. speed cams used mostly on roadworks) appear to flash as I drive towards them, well under the posted limit.

 

As I understand, the SPECS cams are digital video cameras and don't even have flashes, they're just positioned in such a way that your headlights, or the suns reflection from your windscreen, will reflect off the clear plastic lens cover as you approach, causing the illusion of a flash.

 

I know this thread is about GATSOs and TRUVELOs, but I imagine the same thing could well apply.

[Bendy 0]

now i may be wrong here but im sure i've seen a truvelo camera flash, and northampton has loads of them, was behind a car the other day and it was def a flash, and it was pitch black at the time so a bright white light was either aliens invading or the camera flashing!!!! but im sure someone will come along and prove me wrong!!!!

[Bendy 0]

It's a clever rumour that's got out that they use IR light - this is not the case. They simply have a dark red cover over the flash, which stops them from blinding the driver if it goes off at night.

 

In anything except bright sunlight you should be able to see it flash. Although don't expect it to be as bright as the Gatso camera flash.

just got this off a "friend" in the cid department so hope that helps