Speed Trap radars

Pherekydes

Sizzler wrote:

Dont fancy getting done for driving at 62kmh in a 60 zone

It won't happen. You won't get a ticket unless you are 10% over the limit.

Idleater

Slow coach wrote:

It won't happen. You won't get a ticket unless you are 10% over the limit.

Again, not true. The law can be applied at any point at or above the Legal Speed Limit.

The 10% "allowance" is I believe, a myth. (Apart from in eg the States where the cops give you 5% margin of error and the machine 5% margin of error.)

L.

Mc-BigE

I bought a detector last year and everytime a passed a automated "SLOW DOWN" sign the rador would pickup the signal from the gun on top of the sign.
and i pass about 4 or 5 of these everyday going to work, so i first turned it down and finally unpluged it and don't use it anymore. waste of money.
the last straw was when i passed a Garda speed trap on the side of the road (doing 100kph) and the laser detector part didn't go off! and his gun was pointing straight at me!

Glad i found out while doing the speed limit. (which i always do by the way;) )

Anan1

Mc-BigE wrote:

Ithe last straw was when i passed a Garda speed trap on the side of the road (doing 100kph) and the laser detector part didn't go off! and his gun was pointing straight at me!

Glad i found out while doing the speed limit. (which i always do by the way;) )

I'm assuming your detector was dash mounted? This can be a problem with laser, as the beam is very narrow and the Guards tend to use the front reg plate as a target. This is why units such as the M10 Blinder have two sensors, which they recommend installing as close as possible to the front reg plate.

Pherekydes

nereid wrote:

Again, not true. The law can be applied at any point at or above the Legal Speed Limit.

The 10% "allowance" is I believe, a myth. (Apart from in eg the States where the cops give you 5% margin of error and the machine 5% margin of error.)

L.

I'm not saying it's a fact, I'm just saying it probably won't happen. Because of the error in a speedo, the Gardaí cannot prove you are speeding unless you are about 10% above the limit. You go to court and claim you were observing the limit as displayed by your speedo.

MrPudding

With regards to the error on the speedo, how far out are they now? I have come accross a number of those "watch you speed" signs that give you a readout and my speedo is spot on everytime I check.

MrP

Sizzler

Slow coach wrote:

It won't happen. You won't get a ticket unless you are 10% over the limit.

Ehh it will happen, I know at least 3 people that were done by over zealous coppers for 4-6kmh over the limit.

Sizzler

Slow coach wrote:

I'm not saying it's a fact, I'm just saying it probably won't happen. Because of the error in a speedo, the Gardaí cannot prove you are speeding unless you are about 10% above the limit. You go to court and claim you were observing the limit as displayed by your speedo.

Worth a shot if you ask me ! Have read plenty of cases where ppl have gone to court and the case was thrown out cos the cops hadnt had the gun calibrated(serviced) in the last 6 mths. Result ! The problem is people dont take the chance of going to court as they are afraid they will get hit with 4 pts instead of 2

Alun

MrPudding wrote:

With regards to the error on the speedo, how far out are they now? I have come accross a number of those "watch you speed" signs that give you a readout and my speedo is spot on everytime I check.

Wouldn't surprise me if the sneaky buggers added 10% onto the reading just to try and frighten you

My car's speedo, as do most others, consistently reads 10% faster than I'm actually travelling as measured by my GPS, so a few km/h over on the speedo reading isn't going to get you caught. If it does, then there's something seriously wrong with either the speed gun, it's calibration, or the way it was being used, none of which would entirely surprise me.

Pherekydes

Sizzler wrote:

Ehh it will happen, I know at least 3 people that were done by over zealous coppers for 4-6kmh over the limit.

It's not the amount, it's the proportion over. 44 is 10% over 40, 66 is 10% over 60, 88 is 10% over 80 and 132 is 10% over 120.

Do we have any 40 zones?

Sizzler

Yup, theres a residential area for 40 kmh coming from a 60 zone near me...prob implemented by the council though!

elexes

MrPudding wrote:

With regards to the error on the speedo, how far out are they now? I have come accross a number of those "watch you speed" signs that give you a readout and my speedo is spot on everytime I check.

MrP

i rember readinding somewhere about if you change your wheel size the dial will not be fully accurate . so it could give a faulse reading

cargrouch

Ya, if you put on wheels with a bigger outside diameter than the original set then you will cover more ground for every turn of the wheel. So although your speedo says 80, you will actually be travelling faster. You can fit bigger alloys and lower profile tires to keep the outside diameter close to the original. There are online calculators to figure it out. THe calculators will also give you a percentage error for your speedo after the change. But this will add or subtract to the original error of your speedo. Although I presume newer digital speedos are more accurate across the range than old school needles...

The 10% allowance is followed by at least one member of the force that I know - in good weather conditions, eg dry road, and as long as the driver is not driving dangerously/aggressively eg weaving, driving up peoples @rses. Potentially controversial exception - I have heard it said that any boy"wannabe"racers do not qualify for this allowance:D I would say it's more of a rule of thumb, and up to the individual garda...

Idleater

Slow coach wrote:

...You go to court and claim you were observing the limit as displayed by your speedo.

Again the "ignorance is no defence" comes into play.

By your reckoning, I could for example just set my speedometer to read 0-10kmph. Then set off and drive at 150 all the way...

"eh yeah officer, I was just driving according to what I believed was the speed as indicated by my speedometer - I think it was of the order of 8kmph":rolleyes:

No. As the driver of a vehicle, you drive in accordance with the rules of the road, in a vehicle that is suitably provided for in accordance to legislation.

The lenience and allowances given by Gardai et al, are just merely that, personal decisions. I think they have every right to "do" drivers for every infringement but if they choose not to that is up to them not to do so, not up to drivers to break the laws with guaranteed impunity.

L.

Alun

Although I presume newer digital speedos are more accurate across the range than old school needles...

Wrong. They're driven by exactly the same mechanisms as all modern speedos, i.e. electronic sensors. In any case, on modern cars with "analogue" speedos, even these are driven by electronics in the instrument cluster, and not long cables like in the "olden days". I guess the 10% over-reading is added in by the instrument cluster electronics.

Note that what we're talking about here is not a 10% allowance given by the gardai on their speed cameras, but an inherent inaccuracy in the speedo reading itself. If you're travelling at an indicated 110km/h, say, then in reality you're actually travelling at approx. 100km/h, so exactly at the limit. So, in theory, if the cops are excercising a 10% allowance, you could probably drive at an indicated 120km/h in a 100km/h limit and still get away with it, since the speed cameras measure your speed, not what you're seing on your speedo dial.

Seth Brundle

Sizzler wrote:

Worth a shot if you ask me ! Have read plenty of cases where ppl have gone to court and the case was thrown out cos the cops hadnt had the gun calibrated(serviced) in the last 6 mths. Result ! The problem is people dont take the chance of going to court as they are afraid they will get hit with 4 pts instead of 2

How did the calibration of the gun com e into the courtroom? I thought it was pretty much irrelevant as a defendant has to prove they are defective - the gardai don't have to prove anything as the law states that the equipment works fine, full stop.

cargrouch

Alun wrote:

Wrong. They're driven by exactly the same mechanisms as all modern speedos, i.e. electronic sensors. In any case, on modern cars with "analogue" speedos, even these are driven by electronics in the instrument cluster, and not long cables like in the "olden days". I guess the 10% over-reading is added in by the instrument cluster electronics.

OK, I made two assumptions before I posted that:
1) Analogue speedos are driven by induction motors (in the past I believe this was true) whether or not the input signal is from a digital sensor.
2) Induction motor speedos would not be accurate at all speeds.


It's the "control" of the analogue speedos that I was putting the innaccuracy down to. I think that the digital info coming from the sensors will be fairly accurate,and if you plug that into a digital speedo then you don't lose any accuracy. The only source of inaccuracy is the digital sensors.

But if this info is then converted to drive an induction motor then accuracy will be lost. That is, you now have two sources of inaccuracy - the digital sensor, and the analogue speedo.

Now, if my basic assumptions were wrong then obviously the rest of it is rubbish. But even if they were right I could still be talking out me @rse. And even if my theory is right, one or other of the inaccuracies could be so small as to be inconsequential - so all in all, I'm prepared to admit that my post had a fair potential to be wrong! (Or almost right:) )

Savman

And of course the Gardai are infalliable :rolleyes:

Alun

cargrouch wrote:

OK, I made two assumptions before I posted that:
1) Analogue speedos are driven by induction motors (in the past I believe this was true) whether or not the input signal is from a digital sensor.
2) Induction motor speedos would not be accurate at all speeds.

This is all from memory, but IIRC in the "olden days" there was a flexible shaft that took its drive off a small spur gear in the gearbox. This drove a rotating magnet in the speedo housing. The needle of the speedo was attached to a circular aluminium disc which was close to the rotating magnet, and the whole mechanism was lightly sprung to make the needle return to zero when the car was stationary. The rotating magnet on the shaft induced electric currents in this disc (and therefore a weak magnetic field), and this caused the disc and therefore the needle to rotate. All very inaccurate, and the needle was prone to a fair bit of "wobble", especially at high speeds.

I've no idea what mechanism is used in modern speedos to translate the electronic signal coming from the speed sensor to the physical "needle", but I'm guessing it's a small stepper type motor.

cargrouch

Alun wrote:

This is all from memory, but IIRC in the "olden days" there was a flexible shaft that took its drive off a small spur gear in the gearbox. This drove a rotating magnet in the speedo housing. The needle of the speedo was attached to a circular aluminium disc which was close to the rotating magnet, and the whole mechanism was lightly sprung to make the needle return to zero when the car was stationary. The rotating magnet on the shaft induced electric currents in this disc (and therefore a weak magnetic field), and this caused the disc and therefore the needle to rotate. All very inaccurate, and the needle was prone to a fair bit of "wobble", especially at high speeds.

I've no idea what mechanism is used in modern speedos to translate the electronic signal coming from the speed sensor to the physical "needle", but I'm guessing it's a small stepper type motor.

Spot on, the rotating magnet etc is an induction motor. I was assuming that the digital signal was still converted to drive one of these. If it's a stepper motor then the accuracy should be better.

Pherekydes

nereid wrote:

By your reckoning, I could for example just set my speedometer to read 0-10kmph. Then set off and drive at 150 all the way...

I think we were talking about that grey area between 100% and 110% of the limit, not some facetious example that you just gave.

If you are driving at an indicated 60kph and a Guard stops you and says you were driving at 62kph, do you not think you'd have a reasonable defence?

Seth Brundle

I don't think you have any defence as the garda and their equipment is almost infallible due to legal protection and opinion.
It is a drivers responsibility to ensure they are under the limit - if you are over the limit for whatever reason and for whatever amount, you are over the limit.

Pherekydes

kbannon wrote:

...almost infallible...

...is not infallible.

The equipment they use must be calibrated. Once it is calibrated, it is calibrated for that moment in time. That's it.

As you said, it's a matter of opinion, and you'll always find a different one, if you look hard enough.

Idleater

Slow coach wrote:

If you are driving at an indicated 60kph and a Guard stops you and says you were driving at 62kph, do you not think you'd have a reasonable defence?

No, no you don't. You were driving at 62kmph. The margin of error is actually quite small with the laser devices so it might be accurate to +-.5kmph.

What do you define as "reasonable defence"?

how about something ficticious like:

nereid wrote:

I could for example just set my speedometer to read 0-10kmph. Then set off and drive at 150 all the way...

What do you expect to happen in such a situation. In your world of "reasonable defence" this is a perfect argument to give because you can most definitely claim that you "genuinely" believed that you were only going 8kmph...

L.

blastman

nereid wrote:

No, no you don't. You were driving at 62kmph. The margin of error is actually quite small with the laser devices so it might be accurate to +-.5kmph.

I'm not driving a laser device, or anything equipped with one, though, unless you count the CD player.

Idleater

blastman wrote:

I'm not driving a laser device, or anything equipped with one, though, unless you count the CD player.

Good for you.

You won't be caught speeding by a Speed Trap radar gun from a member of the force in that case...

Don't be caught driving without due care and attention with your laser equipped cd player though...

Those things could take your eye out if you're not careful.

L.

Sizzler

kbannon wrote:

How did the calibration of the gun com e into the courtroom? I thought it was pretty much irrelevant as a defendant has to prove they are defective - the gardai don't have to prove anything as the law states that the equipment works fine, full stop.

Erm NO ! The cops are asked by the defence solicitor to take in the equipments maintenance records, if its outside the parameters of the stated period...eg around 6 mths then the courts opinion is it could not be relied upon hence the case gets thrown out.


eg

http://www.trafficticketsecrets.com/cross-examination.html

Pherekydes

nereid wrote:

What do you expect to happen in such a situation. In your world of "reasonable defence" this is a perfect argument to give because you can most definitely claim that you "genuinely" believed that you were only going 8kmph...

You try that, but I'll decline. If I'm driving at an indicated 60 or 80 in a 60 or 80 zone, and a Guard stops me and tells me I was doing 62 or 82, then I'll politely but firmly state I was doing 60 or 80. If he wants to give me a ticket, then I'll contest it.

You can fiddle about with your speedo if you wish, but I'd advise against it: it's against the law.

Pataman

Savman wrote:

Incorrect, you've about 2-3 seconds to slow the hell down although its not much. Bearing in mind that whoever is operating the laser gun might take 2-3 readings to be sure of your vehicle's speed.

Now if you're bombing it along double figures above the limit then you've no chance in hell of avoiding the trap but if you're a few km over (in which case 2 points is pretty harsh) you should have enough time to reduce speed (isn't that the whole point???)

Wrong. Lasers operate at the speed of light. It is triggered and received almost instantly, definately quicker than you can react.

Pataman

MrPudding wrote:

Not strictly true apparently. The laser used are not highly focused high quality lasers so there does tend to be spill. The detector work by detecting this spill when the beam is focused on another car.

With regards to the jammer. The purpose of it is not to jam the laser until you have passed. That would be stupid and obvious to the Gardai. It only jams the laser for 1 or 2 seconds. At the same time you are giving a warning. When you get the warning you are supposed to slow down briskly. It stops jamming, the gardai gets a successful reading of your car not speading. That is the theory anyway. I would expect the gardai may well be suspicious anyway.

MrP

Not true. At the distance theynormally detect you, the beam is about 1 metre wide. It is usually pointed at the front of the car. Most cars are wider than 1 metre, so there will be no spill.