Copper that done me…
In my Foden, said it was 6%.
smokin’ drum brakes!
yourhavingalarf:
Copper that done me…In my Foden, said it was 6%.
It is a guide line. Clearly copped that did you have his own guidelines. unlucky.
smokin’ drum brakes!
Hang on I thought the whole CD’s in the window thingy was to avoid alien abduction and ■■■■ probing.
You lot will be telling me next my tin foil cod piece won’t protect me from having me nads abducted.
Honked:
Was your number plate going slower than the truck??
PMSL…Nice 1
Neil20:
Captain Caveman 76:
IIRC speed guns operate by sending out radar waves and measuring the “Doppler shift” (that is the difference of the returning frequency to the transmitted one) to determine the speed of the measure vehicle. However, since the measured vehicle is usually moving at a tangent to the measuring device ( you never see a copper stood in the middle of the road!) there is an inherent inaccuracy that must be corrected.Hope that helps.
Won’t be driving Lorries if I can understand this
Think of an ambulance with its siren on approaching you. The pitch of the siren changes as the vehicle catches up to its own sound (a little bit more to it than that, but that’s the gist). If you can measure the change in pitch, you can measure the speed of the vehicle. Now replace sound with radar (RAdio Detection And Ranging) and voila, you have a speed gun.
You need to use blu ray disks now that the police are using HD radar.
ringfur:
Get some C.D. discs on the window. Mount then so they move with the vehicle movement. Has worked several times for me.
Brought to you by the good folks at “urban myths and bar room lawyer bollox”.
It also contains such little nuggets as “if you have no license and you get stopped, just say your L plates must have blew off”, “the law says you can go 5% over the speed limit before the police can charge you for speeding” and the other fans favourite “If you are being questioned by more then one police officer, you can claim intimidation and the case will be thrown out”
Evil8Beezle:
It’s not complex if explained by a good teacher, hence Cavey is now driving a truck!
You boy! I heard that. Detention for you sunshine, with Dipper_Dave! 
Captain Caveman 76:
Neil20:
Captain Caveman 76:
IIRC speed guns operate by sending out radar waves and measuring the “Doppler shift” (that is the difference of the returning frequency to the transmitted one) to determine the speed of the measure vehicle. However, since the measured vehicle is usually moving at a tangent to the measuring device ( you never see a copper stood in the middle of the road!) there is an inherent inaccuracy that must be corrected.Hope that helps.
Won’t be driving Lorries if I can understand this
Think of an ambulance with its siren on approaching you. The pitch of the siren changes as the vehicle catches up to its own sound (a little bit more to it than that, but that’s the gist). If you can measure the change in pitch, you can measure the speed of the vehicle. Now replace sound with radar (RAdio Detection And Ranging) and voila, you have a speed gun.
That’s where we get the super cool difference between Radar and Lidar.
Radar relies on the reflection of radio waves. As they are reflected off a vehicle, if the vehicle is coming towards the emitter, the waves are compressed. This increases their frequency - same principle as a siren’s pitch goes up as it comes towards you. It’s also the key to one of the major failings of radar - long frequency electromagnetic waves cannot stay tightly focused as they travel away from the emitter, so if you try to tag a vehicle too far away, or in too close proximity with another one, the return wave will be scattered giving false or failed readings. The speed calculation is made based on the change in frequency of the return signal.
Lidar fires fikkin’ lasers, so obviously it’s better 
There isn’t a chance that a vehicle can move fast enough to create a measurable Doppler Shift effect in a laser (besides, light is a simultaneous particle-wave, so can’t Doppler ■■■■, but can Red/Blue Shift in the same principle as Doppler Shifting - where wavelength compression/expansion skews white light towards the red (longer wavelength, object is moving away from you) or blue (shorter wavelength, object is moving towards you) ends of the spectrum respectively. So, rambling a little, since cars etc can’t get even remotely close to the velocities required for detecting Red/Blue Shift the measurement of speed has to be done differently. The Lidar unit fires a succession of pulses of laser, probably about 400-600 pulses per second, if I remember correctly. The unit then measures the change in return time of the pulses to figure out how far the vehicle has traveled… and then essentially doing an old school speed = distance / time equation on it. There will be a threshold count of return pulses that the unit will need to receive before it’ll perform the calculation, but typically it’ll only need 100ish return pulses - so results in well under a second. Also, thanks to frikkin’ lasers, being only nominally degraded by air, the device can be considered line of sight - the only limitation being the user’s eyesight or the horizon.
In both cases, vertical, flat surfaces provide the best return wave - hence aiming a Lidar unit at a numberplate, and aiming a Radar unit low-ish on a car… but with a lorry providing a massive flat front, it’s not going to be that much of a challenge to get a return signal! The angle of incidence, in both cases is important to the quality of the return waves. With Radar, and it’s long wavelength waves that emit from the unit and then again off the vehicle, they ripple out in 3D, so you can be offset and still capture the return wave. Lidar’s short wavelength doesn’t ripple out in the same way, so angle of incidence becomes more important to being able to capture a return signal, however the increased distance at which it’s effective means that the angle of incidence is reduced anyway.
Neither device will be affected by hanging a couple of CDs behind the giant expanse of electromagnetic wave-reflecting glass
Well it’s all too complicated for me. Since I was up to 8 points many years ago, I’ve driven like a vicar in an Allegro.
PS, did anyone else notice today that they’ve taken the fixed cameras down at Kidbrooke on the northbound A2 and replaced them with average speed cameras?. I’ve been away for a week so apologies if it’s old news.
ringfur:
Get some C.D. discs on the window. Mount then so they move with the vehicle movement. Has worked several times for me.
If all it took to avoid radar returns was CDs, then the military would be coating typhoons in unwanted Cliff Richard albums 
What about a radical approach like doing 40 in a 40 zone etc and not coming on here asking if you’ve been done. Jeffinf idiot.
peterm:
What about a radical approach like doing 40 in a 40 zone etc and not coming on here asking if you’ve been done. Jeffinf idiot.
You’re ■■■■■■■ into the wind trying to explain that logic on here mate.
Ive been involved in many a dingdong on here saying that and many of the “professionals” cant see that maybe thats the best approach and instead keep breaking the limit and then look for loopholes.
Freight Dog:
ringfur:
Get some C.D. discs on the window. Mount then so they move with the vehicle movement. Has worked several times for me.If all it took to avoid radar returns was CDs, then the military would be coating typhoons in unwanted Cliff Richard albums
Cliff Richard cd’s of course wouldn’t work, you needed Des O’connors …
ringfur:
Get some C.D. discs on the window. Mount then so they move with the vehicle movement. Has worked several times for me.
In a word RUBBISH,you was obviously not over the speed limit as you thought you was.
CD Disc in the windscreen is just an old drivers tale concocted in some RDC Drivers room
Neil20:
Hi all,
Just coming back to yard after work and I face police speed gun on 40mph zone. I’m sure I was doing 45 when they spotted me, facing gun at my lorry for 5-10 seconds. but I put my brakes on and within few seconds I was under the speed limit. Can’t figure out weather I got caught or not…
If they put gun towards ur number plate which speed does they count ?
40 red circle limit zone 
ROG:
Neil20:
Hi all,
Just coming back to yard after work and I face police speed gun on 40mph zone. I’m sure I was doing 45 when they spotted me, facing gun at my lorry for 5-10 seconds. but I put my brakes on and within few seconds I was under the speed limit. Can’t figure out weather I got caught or not…
If they put gun towards ur number plate which speed does they count ?40 red circle limit zone
Yes it is.
A friend of mine is a copper he let me have a go with the speed gun a few weeks ago it’s just a point and pull the trigger and the speed pops up instantly. He said he doesn’t normally pull people unless there a good bit over the limit mind so doesn’t pull many folk.
I asked him what was in the camera bans and he said same thing but on a tripod with a camera attached, so whether your caught or not all depends on if the operator is paying attention and how quick they are. Or if it’s a copper not a van if they actually want the paper work for chasing it up
Other ways of measuring speed uses 2 square marks on the tarmac, as you pass the first mark, the police flick the switch on the recorder, when you pass the second mark, they flick the switch again, this gives them your average speed between the 2 marks. That’s for those who wonder what the paint marks on the tarmac are for. 
Captain Caveman 76:
Evil8Beezle:
It’s not complex if explained by a good teacher, hence Cavey is now driving a truck!You boy! I heard that. Detention for you sunshine, with Dipper_Dave!
Give 'em 500 lines apiece - “I must not be clever dickie on Trucknet” and then the detention with expressly no mags for Dipper. 