Speed Enforcement Devices

[Cryozombie]

I have sort of a weird question, wasn't sure where to stick it, so I thought I'd ask here...

Around here it is common to see devices that local LEOs put out, and move to different streets, which are basically a box, with a Speed Limit sign on the front, and a big digital readout that shows you how fast you are going. If it detects you speeding, it flashes your speed and a strobe to get your attention. They aren't ticketing devices, just safety devices.

Recently the city began testing Speed Cameras for issuing citations.

Here's my question:

I was coming home from work in the wee hours of the morning, was the only car on the road and stopped at a red light. Directly across the intersection from me was one of the Safety Warning devices, and despite the fact I was sitting at a dead stop at a red light, it was displaying me at a speed that was fluctuating from 7-9 mph. As I said, there were no other cars at the time, just me, so I know it couldn't have been reading another vehicle. This being the case, should the idea of a Speed Enforcement cameras be a concern? I'm concerned that if a car going 0 can be recorded at 9, whats to say a car going 30 cant be clocked at 39? Or is this just a fluke and not something to even be worried about? I've never really noticed any serious inaccuracy from these devices before, unless I was on my Motorcycle, and I always attributed that to the small profile of the bike compared to a car... But now I'm wondering how reliable these devices actually are.

 

[jks9199]

It's kind of a complicated question. An actual enforcement device has to meet certification standards. These test its operation sure it's working accurately. The classifiers that simply track speeds in traffic volume then record for Speed surveys aren't quite calibrated quite the same way. In the new people signed to tell you to slow down map to calibrate it all really. In the case you described, I suspect it was actually reading your motors fan or something like that , though it could have been a few other things as well.

Sent from my Galaxy Nexus using Tapatalk 2

 

[Dirty Dog]

Best thing you can do with those gizmos? Measure off 1/4 mile in front of them....

Not that I've ever done that, of course...

 

[rlobrecht]

My city put a number of permanent versions of these around my neighborhood, all in 30mph zones. I can set my cruise control on 30, and see readings from 28 to 33 while driving around.

 

[Carol]

I have seen an unusually high reading from one of those digital readout devices. My band plays at a VFW hall on Fridays that is in the middle of nowhere. I keep my cruise locked on 30 because I have to drive through long residential stretch before I can get out to the highway. I have seen on at least one occasion the device in that neighborhood blinked at me with a 39 MPH readout and as far as I know I was also the only one around.

I don't recall seeing that kind of odd reading when I have driven by them in other areas.

 

[Tgace]

Hmmm..what if it catches a speeding car passing a car doing the limit. 2 cars in the shot, how can you tell which is the culprit?

Its been a while but when I went to radar school they taught us about all sorts of errors to look out for. "Look Past Errors", "cosine Errors", "double bounce errors", etc. When you are operating the device in person you can discern it when it's happening...I don't see how these "speed machines" could survive a court challenge. Of course, they bank on the bulk of people just paying up.

 

[arnisador]

They're all over the base I live on--solar-powered and accurate at driving speeds.

 

[Carol]

Best thing you can do with those gizmos? Measure off 1/4 mile in front of them....

Not that I've ever done that, of course...

You need to borrow some sunblock there, Dirty Dog? Your neck is startng to look a bit red :lol:

 

[Dirty Dog]

You need to borrow some sunblock there, Dirty Dog? Your neck is startng to look a bit red :lol:

Nothing redneck about drag racing... ask Gemini... And it's not like I'm doing it in an '87 Dodge Ram pickup while someone holds my beer. My Dodge Ram is a '98, and it's for offroading, not racing. :rofl:


When I race, I do it in a Corvette. Trap speed is vital when you tweak things. ET can vary widely because of lots of factors (traction, for example). But changes in your trap speed will directly reflect changes in power.


Years ago, using those traffic monitoring gizmos was actually useful for checking things after tweaks. Nowadays, I use an iPhone app that measures acceleration, 0-60, 1/4 mile, braking, lateral gforces, etc. Much better.

 

[punisher73]

Saw this joke posted today and thought it applied here. Hope you enjoy...

A man was driving when he saw the flash of a traffic camera. He figured that his picture had been taken for exceeding the limit, even though he knew that he was not speeding.... Just to be sure, he went around the block and passed the same spot, driving even more slowly, but again the camera flashed. Now he began to think that this was quite funny, so he drove even slower as he passed the area aga...
in, but the traffic camera again flashed. He tried a fourth time with the same result. He did this a fifth time and was now laughing when the camera flashed as he rolled past, this time at a snail's pace...

Two weeks later, he got five tickets in the mail for driving without a seat belt..