Those roadside speed indicators - how accurate for you?

[map]

Went down the A19 towards Doncaster the other day.

In some of the villages (Askern/Toll Bar/Bentley) they have those digital speed indicators on lampposts. Shows speed in green if 30mph or below, in red if above.

Now approaching one on the bike. It didn't switch on until I was quite close. Then showed speed as 15mph

So not much use then with bikes. Maybe more accurate with a car/van/4x4/etc. Bike was the CB500 commuter but I'm not exactly small (see avatar!).

Also got me thinking is it the same technology as police speed guns? So could it read way over as well as way under? Maybe they're laser and the lamppost ones aren't. Still, I'd image from a small, curved (non flat) surface like a bike even a laser could get scattered and give incorrect reading.

Although I expect police to say something on the lines of "we've had training, it's calibrated, prove us wrong, no we won't give you any help or information to do that"
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[pinkyfloyd]

Not sure how they work but we have one of the light up ones near the bar I work in that lights up with the 20mph sign if you go past too quickly. Trouble is, it lit up at under 20 on the bike. Go figure.
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[barrkel]

There are a number of them in Essex on approach to villages.

I find them accurate, if they pick me up coming down the road - GPS accurate. If they don't pick you up until the last moment, then they're often not very accurate.
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[Shinigami]

these very often don't pick up my fazer at all
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[GeorgeB.]

There's one in a 30 zone, on a straight road that I travel on frequently. Legend has it that on a CB400 it tends to be 99% accurate, however over 40MPH it doesn't detect you at all.

How weird
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[Rogerborg]

Lowest bidder tat, it doesn't need to be accurate, it's just there to wag the stern finger of disapproval.

The nearest one to me shrieks "SLOW DOWN!" when I approach it on a pushbike. Uphill.
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[mentalboy]

There is one in town, which only flashes up for the Zed at night time.
It often makes me chuckle when I've just booted off the lights in a GP start and booted through it without getting a ticking off knowing full well that little Johnny in his souped up Saxo will be wondering how the hell it ticks him off at 35 despite the fact I have just burst his eardrums and been ignored by it
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[Nobby the Bastard]

They seem to need a higher speed to be activated when it's raining...
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[talkToTheHat]

most of the ones in the doncaster area won't pickl up a 125 at all and only sometimes register the 190kg of mostly steel that is my 535. Mostly they register the car behind. Similar problem on a 125 with some traffic lights that only operate part of the sequence if vehicles are waiting to turn

[yen_powell]

I put some of those in either side of a school last year.

The manufacturers set them up how the council want them after they are fitted and the power supply plumbed in. I had them set to over read by 5mph, so if someone is doing 25 it flashes up 30 etc.

To be honest I'm not convinced of their effectiveness. If I'm going to slow down it'll be for a proper safety related reason, not because a sign tells me to.
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[Benno]

[MC]

[bikertomm]

Oh that thing,

I thought that was points?

A special kind of leaderboard?
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[Joncrete Cungle]

I like to wait for it to pick me up approaching, then grab a handful of throttle, endanger a brace of kittens and chuckle to myself as the speed reading increases then turns to 3 horizontal lines.

[Kickstart]

Hi

Never really checked on a bike, but in the car at the best they manage to flash up a speed equal to the indicated speed (which I know to be high).

All the best

Keith
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[Commuter_Tim]

[bikertomm]

[FretGrinder]

Inb4 "they usually give you +/- 10% +2 *^10 - 2 mph"
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[DrDonnyBrago]

They tend to match the speedos of my cars, don't often get my bike.

[Baffler186]

[NooBish-AbbZ]

rarely pick me up, if they do for example they say I'm doing 34, bike says 37
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[Davie J]

Do they still flash -- and need reset if you go past them doing over a ton?
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[kris84]

There's one when you approach pool-in-wharfedale, said I was doing 31mph, speedo said more like 39... do speedo's normally over-compensate?
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[Kickstart]