Speed check points accuracy?

[User16625]

I got clocked by one of those speed check devices the police put on lamposts to tell car drivers how fast they are going before entering a built up area. Most of the time my bicycle doesnt even trigger them so am wondering how accurate these things are. Any ideas if they are any good at measuring a cyclists speed accurately? They are intended for cars after all.

 

[ohnovino]

When I've set them off they've always been within 1-2mph of the speed on my computer.

 

[gavroche]

I went through one that indicated 28mph, exactly the same as my computer.

 

[asterix]

Most seem accurate enough but I know one that triggers at 28 by my speedo which itself almost certanly over-reads.

 

[gaz]

They are pretty accurate. You just ain't fast enough to set one off.

 

[marinyork]

They are reasonably accurate but do malfunction sometimes. One up the road use to say things were doing 88mph. The 'slow down ones' there's one near me that they have to recalibrate as it drifts off a bit every so often.

Most of the ones I've clocked on my bike it's said 12mph which I just thought was funny in itself

 

[pepecat]

My dad got clocked by one not so long ago. He was doing 4mph.
He was out running.

 

[Tyke]

I got clocked at 21 today bike comp said 21.5 so they are very close, might be more likely to be bike comp that's out if anything.

 

[Fnaar]

I go past 2 of them on my commute into work. One is on the flat just at the top of a hill. It usually says 14mph to my bikes 13. The other is one a slight downward slope, and I usually hit about 23-24 there, and it tallies more or less with the bike comp.

 

[PoliceMadAd]

I clocked one earlier, told me i was doing 7mph :L

 

[sheddy]

My dad got clocked by one not so long ago. He was doing 4mph.
He was out running.

How big is he ?

 

[byegad]

I set one off yesterday. It was a limit warning sign rather than a 'Your Speed'. At well under 10mph it triggered the sign telling me I was over 30mph. The last time i drove past it in the same direction it ignored me at 28mph??? How do they work?