Safe Speed Forums

I am in process of defence so cant identify place or my name.

I was stopped for doing 113 mph at 385m. I vehemently deny this. Took PSNI 6 months to summons me. At stop site I observed LTI showing 113 which is a positive figure. Circumstnces are that only possible observation point was a bridge c 4 km back.
PSNI revealed bridge I suspected but not exact position.
I year later they reveal "top of slip road" and not vertically over bridge over 4 lane motorway.
I discover at exact time of observation the SUN was exactly in line of sight (no + or - error) so I proceeded with my defence.

At first hearing PSNI now allege top of sliproad on exit of roundabout. ie they were watching me recede from roundabout.
Summons shows clearly "approaching fromXXXXXX"

Under cross examination policeman admits LTI 20 20 Ultralie has either a + sign for approaching traffic and a -ve figure for receding.
He admits he did not show me a -ve when stopped (I did not observe any -ve) and admits he did not include the -ve figure in the summons.

His excuse was that he did not have a degree in english. he waqs traffic policeman for 10 years surely he knew how to word a summons with a +ve or -ve figure.

Naturally I am now highly suspicious of the process and my trial.

I now wish information technical\on the infamous device. I will reveal more next post.

Hi mysterious one.


What speed were you really doing? (I guess you can be truthful being as you haven’t broadcast any personal info).


Would I be right in assuming the sun was in the same vertical plane as the beam but not in the horizontal plane? If so then it’s of no relevance.


That’s correct. “For approaching targets the speed will display a positive figure whilst for receding traffic the speed display will be preceded by a negative (-) sign.”


If you were receding and the speed readout didn’t show a negative sign then it seems you have a case, but I need some clarification before I can confidently say that:

* Were you going toward or away from the equipment when your speed was taken?
* How did he show you your alleged speed?
* Have you seen, or do you have a copy of the evidential photo/video?

Initially my defence was based on fact Officer was observing traffic "approaching from xxxxxx" and fact speed of 113mph was on summons. 113 mph is NOT -113mph. It is therefore +ve.

Now I have to defend myself from an officer who alleges "approaching from XXXXX" actually meant receding from roundabout and that he did not record -113 mph on summons or show - 113 mph at stop site because he beleived I would not understand a -ve figure.

I state now that I had c 1 minute to observe the screen and observed no - or + figure.
I am a ex BT telecom engineer.

Bear in mind this summons was made out by a traffic officer of 10 years experience. He said he had no degree in English. However Receding and approaching with respect to a Radar detector are words which are clearly on the ACPO Code of Practice PDF.

I believe I am being stitched up.

see next post

So how about answering one or two of smeggy's key questions, like what speed were you actually doing?

To be honest, having watched a few cases in english courts, you havent a chance with the +tive/-tive defence. I have seen solid defences ignored over +7mph. If you have not got a rock solid defence. you ought to consider pleading guilty to a lesser speed in what is called a "newton hearing" There is loads of stuff on www.pepipoo.com
If you could get the court down to a lesser speed and say sorry you might even keep your liscence.

Even at 113 people have kept thier liscence others have had 28-56 day bans.

What speed were you doing?

_________________
Speed limit sign radio interview. TV Snap Unhappy
“It has never been the rule in this country – I hope it never will be - that suspected criminal offences must automatically be the subject of prosecution” He added that there should be a prosecution: “wherever it appears that the offence or the circumstances of its commission is or are of such a character that a prosecution in respect thereof is required in the public interest”
This approach has been endorsed by Attorney General ever since 1951. CPS Code

Either you've misunderstood lettherebelight or I misunderstand you, but he would have a solid case if the direction of the measurement can be proven to be incorrect.

I've just noticed LTBL's description of the gun (which BTW is not radar):



LTI 20 20 Ultralie

Ultralie 100 uses a train of 100 pulses of light sent out over 0.4 to 0.3 seconds. Each pulse consists of light sent out from a laser light generator which has a wavelength of 904 nanometers. The laser is a class 1 device which means its output is less than 3 mW per m squared.
This converts to 3 E -7 W cm.

The beam diverges at 3 millirads.
(Explanation A circle has a radius of 1 meter. Along the circumference you measure 1 meter from point where radius intersects circumference. Draw back to centre another radius. You now have a triangle with an angle of 1 rad. Since circumference is 2 PIE R and since 2 pie r represnts 360 degrees it folows there is 2 pie rads in 360 degrees

Thus in circle of radius 1 meter 1 rad has 1 meter on circumference. 1 millirad equals 0.001 meters and 3 m Rad would be 3 mm (0.003)

Now if LASER BEAM is measuring at 380 m then 1 rad on circumference would be 380m and 1 m Rad would be 0.380 and 3 m rad would be 3 x 0.380 which is 1.14m.

In other word the power of laser is now dissipated over an area of diameter 1.13m

1.14 m is almost the width of the rear of a car which in this case is 1.4 m.

Area of circle of diameter 1.14m is PIE RSQUARED

Area is 10208 cm 2

Now if initial power was 3 e -7 then 3e-7 divided by 10208
= 2.83 e-11 W cm -1

This is exceptionally low


Now since a blue car absorbs all light and converts to heat except for blue wavelenghts then only the number plate "reflects"

A number plate is 52 by 11 cm which is 572 cm

The lettering on numberplate does not reflect thus only about 60 % reflects or c 400 cm 2

Thus total reflected is 400 x 2.83 e-11 is 1.132 E .8 W cm-1

Am I right smeggy?

Now simplistically a number plate reflects straight back to sender BUT at a cone of divergence of 4 degrees from beam origin

When the beam arrives back it covers a circle of diameter

Now 2 pie rad = 360 degrees
pie rad =180 degrees
1 degree = pie /180 = 1degree is 0.01745 rads (1.7 m rad)

therefore 4 degrees = 6.98 m rad

Since in this case measurement was 380 m which is 1 rad and 1 mrad = 0.38 or 38 cm

then 38 x 6.98 =265.24 cm or diameter of 2.65 m

Now area of circle of diameter 2.64 is 1.75 = 96224 cm 2

Thus power from numberplate is dissapated over 96224 cm minimum

2.83 e -11 divided by 96224 cm = 2.94 e -16 W cm

Now lens collects c 10 cm 2 so 2.94 E -15 W cm falls on light detecting device

Convereted to W m2 this is 2,94 E -11 W m 2

This is roughly 10,000,000,000,000 times less powerful than the light sent out from the laser.

Now in certain circumstances light can reflect off the shiny surface of a numberplate. Numberplates differ from motorway signs in that the reflective glass beads are covered in shiny acrylic plastic.

Since the SUN contains every wavelength including visible light and invisible IR at 904 nanometers IS IT POSSIBLE THAT A REFLECTION OF THE SUN can overwhelm the 2.84 E-11 W M2???????


Now Sun as measured near surface is approximately 1400 W m 2 of which 9 % UV 41 % Visible and 51 % IR of all wavelengths

Thus a perfect solar reflection would be circa 100,000.000,000,000 more powerful than expected.

Perhaps this is why ACPO explains that device should not be pointed into the SUN

What does Smeggy think of overwhelming the casacade effect photo detector?

Now point of observation is edge of slip road ie 60 m away from centreline of outside carriage way

Since this is c 190 ft which is c 180 ft more than ACPO recommendation of "10 ft from carriageway being measured" there is some concern.

Now trigonometry of triangle adjacent of 60 and hypotenuse of 385 m produces a distance of 380 m on carroiageway.

Since time from time final and time initial is 0.4 seconds and alleged v = 113 mph or 180 km hr which is 50.2 m s it follows that car travels 20 m in 0.3 seconds

Thus inital acquisition point was 360 m c 8.95 degrees wrt car

As viewed from observer this entails sideways movement of 3.11m (sin 8.95 x20 (acquisition distance)

This means a SLIPPAGE of 3.1 m in 0.4 ms or a sideways movement of c 19 mph.

Can anyone explain how a policeman can move sideways accurately in exactly 0.031 m or 3 cm increments with 0.004 intervals when the human brain CAN only react to any stimulus in 0.5 seconds

Remember the THINKING DISTANCE ON THE BACK OF THE OLD HIGHWAY CODE.

Even if numberplate was accurately observed the plate would move relatively from right to left in c 0.1 seconds and it would take 0.5 seconds to realise this had happened.

Does anyone have an accurate source of Human Brain reaction time?

if i cared... and could follow your maths.... i'd comment.

but i don't and i can't sorry.

and if i can't.. good luck explaining it to the judge

To be accurate, the LTI sends out around 43 pulses, but this is irrelevant.


You missed the trick. The trick is within the definition of a class 1 laser - there is a time dependency of how much energy density you can emit. So long as the average power conditions are met for 250ms, then you can output any impulse intensity you wish. In the case of the LTI2020, it can output up to 34W peak power.


However, there is a narrow IR filter in line with the receiver diode which would absorb most of the IR from the sun.


Smeggy thinks it’s not relevant

I don’t have time to check the maths (there’s no point given my conclusion below) but you seem to have applied most of the correct principles. However, you have completely misunderstood my original point.

I completely agree that the sun’s rays on the diode will certainly upset the LTI, in fact it is likely to give you an E07 (jam code). However, you said the gun was ‘in line of sight’ with the sun, but unless the gun was ‘pointed into the SUN’ (again your words) it would have little or no impact – this is what I was trying to clarify so there was no need for you to go off on one.....




If the gun is aimed at the hemisphere toward the sun, will be inline with it in one plane regardless of where you aim it. This is not the same as aiming directly at the sun; that’s the only time your maths will apply.



Your rudeness is quite offputting. I was only trying to help you but I will no longer be doing that, that’s your loss because you greatly underestimate my abilities and knowledge, which is a shame because I really can help you.

by the way.. i'm not sure whats so complicated about radians.. its just a measure of angle.... apart from the definition i'm not sure why you have to reference it to the radius/diameter (words which you disturbinlgy use interchangeably.. lets hope there's not a factor of 2 missing somewhere in your working)?

OK, I’ve been though the maths. Lettherebelight, you are waaaaaaaaay out, and when I say waaaaaaaay out I mean much more than an order of magnitude of an order of magnitude!!!!
You’ve made basic math errors at most stages, some of them horrific.
You’ve also made the most horrendous of assumptions (and yes, ed_m was indeed right with his suspicions).

If you want help then try not to tell us what to think, and if you do then please don’t embarrass yourself by getting it so very, very wrong!
That’s what you get if you play at math with the big boys


What does Smeggy think of noobies overwhelming us with BS?

i am at a complete loss as too how I have been rude. If I have I apologise.

Second I explained that my original belef was that observation was made directly into the SUN. That would entail reflections off car rooves and windows as cars approached. However PSNI now allege the observation was made exactly in the opposite direction. That is now irrelevent.

Thirdly I have never been able to discover any technical information on the LTI 20 20 ULTRALIE 100% except for the divergence cone which I assume is correct.

Where does the 43 pulses come from and how long does a train of 43 pulses take?

Fourthly there is no information on the technical output of the laser used in the LTI. Where does the 24 W Peak power come from?

Does anyone know exactly what is output from device in W cm 2

If my mathematics is wrong wrt to divergence assuming now corrected to 24 W m 2 from a source of 1 cm 2 what would it now be?

If LTI is observing receding traffic ie going away from the police and it registers 113 mph ie positive with NO -VE sign surely the only way this can result is from traffic approaching.

Without a handbook and with no information from the Home Office or the police how can I defend myself?

I can now prove there is a substantial component of right to left movement which would involve SLIPPAGE which is mentioned in ACPO COP.

I have a lettert from Home Office stating "there is no hardware or software developed to prevent slippage and no software updates"

Same letter states the device was never tested in wet weather, fog, sunshine or over wet grass before a licence was issued

If you have any source of information I would appreciate it if this was revealed

SUN
sINCE MY ORIGINAL DEFENCE WAS SHOOTING INTO SUN and now my defence is about a car going 180 degrees directly away from the SUN it turns out the mathematics are such that a reflection occurs OFF the acrylic numberplate using SNELLS LAW.

whatever my mathematics of a cone of diverging light from the laser it is a fact the return power must be significantly lower than emitted. Any SUN reflection from the acrylic surface (not the 3M retroreflective surface at rear of numberplate) must be significantly higher than the dispersed, absorbed, reradiated and dispersed light emitted by the laser.

And yes the numberplate is tilted back at angle which is exactly at right angles to the declination of the SUN and yes the angle as viewed from above is 8 degrees between SUN and direction of movement of car and 8 degrees between direction of movement of car and observer which satisfies SNELLS LAW of angle of incidence being equal to angle of reflection.

I don't think this argument flies. In the real world of laser speed meters, it's a very fast rising edge that is detected. It really doesn't matter if that rising edge stands above darkness or above a background that is a million times brighter. If the rising edge can be detected (and clearly it can), then arguments of relative brightness are irrelevant.

Slip effect is much more likely and much more sound as a defence.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

If you are at a loss as to how you were rude then I am at a loss as to why I should aid you. However, helping you would serve the common good so perhaps I should persevere.

For me to help you must answer the questions posed in my first post.

If the reflected (not direct - now we are getting there) sunlight really was a significant problem, then the gun would have been generating error messages and the operator would simply have moved position to reduce the frequency of occurrence.
The algorithms simply won’t allow false speed readings from such sources; no source of reflection will cause the sun to be pulsed ~40 times, all with clean edges, all with a regularity within nanoseconds. Even if there is such a source, it would have to be synchronised with the output beam – literally a 1 in a million chance.
Blaming false speed readings on reflections from the sun is a non-starter; you will be laughed out of court, rightly so I'm afraid.

As for my sources: I have various LTI documents in my possession stating the relevant information.

Paul is absolutely correct. The LTI receiver hardware has adjustable reference levels such that it can discriminate the received laser pulse edges (surprisingly powerful BTW, you need to redo your maths) against significantly high, relatively static, background levels.

I still would welcome an answer as to what speed you believe you were doing when the trigger was pulled. It said 113. If the angle was significant, cosine would suggest a true speed of more if there was no slip, eg, 120.

What do you believe you were actually doing? (Note - not trying to knock the work here, just trying to get things in perspective).

I was doing 60 mph exactly ie 200 rpm on my wifes Bora. In the back I had a family freind who was suffering from morning sickness. I had the window open because she thought she was going to be sick. There is absolutely no question of my car doing 113 mph.
Howe3ver the roundabout is 1.2 km from an exit for an accident and emergency hospital.

How can a \policeman set a device for background IR radiation against a car reflecting using SNELLS Law when it has already been introduced in court that he followed a procedure of alignment with a lampost near the roundabout and then aimed the device. There was NO OTHER PROCEDURE.

If the device is aimed at a car from rear at angle of c 9 degrees the lIR ight will either be absorbed by the BLUE paintwork and converted to FAR INFRARED. The car is blue because it absorbs Violet, Green, Orange, Red and presumably near IR. This is presumably why the police aim at number plate.

furthermore a rear numberplate is YELLOW which means it is at least absorbing Blue and Red in various levels.

Was a European yellow number plate ever tested by Home Office at all and was it ever tested at an angle of say 8 degrees.

I believe American number plates are Aluminium with a coating of Retroflectiove WHITE.
Europen numberplates can be white or yellow BUT they are all covered by a layer of clear reflective ACRYLIC PLASTIC WHICH REFLECTS.

If the output is not c 3mW m2 average but actually is say 30 W m2 short duration peaks (an increase of pulse strength of c 10000) then the length in time the peak is actually ON must be reduced by a factor of 10000.

Either way the strength of the pulse is reduced by the dispersion of the outgoing pulses. it is only the number plate which may reflect part of the beam back.

But I can prove that a significant amount falling on the number plate at c 9 degrees is reflected away from the Observer and not back to observer.

However at exactly at same time as light from laser is reflected away Sun light is being reflected by Snells Law towards the observer.

If a car can produce slippage by moving sideways or movement sideways on a car can produce slippage usually measured on a horizontal plane then surely SLIPPAGE also occurs with the vertical movements of a car as it moves over imperfections on the road surface.

By the way I have a letter from Home Office stating there are no software or hardware modifications to address the problem of slippage.

Smeggy indicates a rising pulse detector. Since a short duration of pulse (100 pps each with on off ratio of c 1:1000 makes a pulse length of c 10E-6 s lenght
If photodetector detects only the rising edge of the ON pulse and not ALL of the pulse then it seems almost impossible to distinguish between a rising edge coming from the SUN/road vibrations and a rising edge generated by an exceptionally weak signall coming back from a absorbing and re3flecting vibrating yellow numberplate.

Recent controversy about policeman doing 150mph on a joyride. What is maximum permissible speed in a non emergency situation by a UK policeman. Is it 125 mph as I beleive.



I