so that part is covered… but i still have some questions regarding the way the cops use these devices to fine me, i.e. the enforcement aspect.
Does every car that crosses the speed limit (even if 1mph more) get fined if caught on cam ? or is it if you are atleast 5mph above the limit ? or is it your speed relative to the rest of the traffic and the top 10% speeders get ticketed ? how does it work ?
my bro says that as long as he is at relatively the same speed as most cars on the road, it’s ok. on motorways that have a 70mph limit i’ve seen him do 80mph regularly and not get ticketed yet.
also, do they, in london, use cameras from behind or in front of the cars ? i’ve been trying to locate the cameras on the motorways but i can never see one. i mean i see the signs saying camera, but i never see the camera.
and, is the driver fined or the owner of the car ?
and, one more question that hasn’t been covered by howstuffworks.com
do the speed guns catch acceleration ? e.g. speed limit is 60mph. i start from 0, do a cool wheel spin, reach 60 in minimum time, and then stay under 60. is a speed gun capable of clocking this kind of driving ? i mean when the radar hits my car it will be accelerating really fast, so the radar gun would clock my speed as very high [since my instantaneous velocity is very high], but i’m actually still under the speed limit. i’m kinda unclear on this point. is there a fallacy in my reasoning ? would someone be kind enough to explain how acceleration is accounted for in a speed gun ?
thank you for answering my kinda long question. i look forward to being a law abiding, and well informed, tourist.
The gun takes about 1000 samples a second so if your car can make its delta really big in 1/1000th of a scond then yes your speed would be skewed, but most likely you would be dead from the g-forces
This is a policy decision by the particular agency, has nothing to do with radar.
Electronic cameras, still or video are very tiny and can often be smaller than the diameter of the lens. Not suprising you don’t see the camera. What, are you looking for a film crew with an Arriflex camera on a wooden tripod?
Again, a policy decision. You are the registered owner of the car so you are identified with that car. If you can provide evidence that someone else was driving your car that may possibly used in your defense.
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Finally, a question actually about traffic radar!.
Velocity and acceleration are two different things. Doppler radar can easily measure both but traffic radar only displays velocity AFAIK. Velocity is by definition an instantaneous measurement. Speed is a measure of distance divided by speed. If that distinction doesn’t make sense to you then you might consider taking physics 101. Doppler radar measures velocity by the difference in the frequency of the return signal compared to the sent signal. It can track velocity over time and calculate acceleration. Why would you think that in accelerating up to 60mph you would ever be measured faster than that speed?
Padeyes post explains how it works, whatI can do is to give some insight to how they’re perceived over here.
I don’t know about London in particular, but thiw is the way it works in Switzerland:
Here, only a fraction of the cameras are actually active at any given time. I don’t know why, but I guess that the desk cops in charge don’t want too much work. :rolleyes:
When the cameras are active, they generally have a threshold, 5km/h above the posted limit. Every car going faster than this gets fined. I was once next to a busy motorway, with a new speed camers, and it kept flashing about every five seconds!
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Again, I don’t know about London, but in Switzerland they are humongous concrete blocks, by the side of the road, photographing the rear number plate. (What I really hate about this, is that they’re pretty obvious if you know where they are. => locals know where they are, and only tourists get fined.)
In Sweden they use smaller cameras on poles, photographing the driver as well as the front number plate.
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As Padeye pointed out, it’s in theory the driver who’s responsible, unless he can point the blame to someone else.
As to your fourth question I’m as stumped as Padeye…
[sub]Keyboard problems? There are normally two shift keys, one to the left, between [Ctrl] and [Caps lock], and another to the right, between [Ctrl] and [Enter].;)[/sub]
ok, lemme thank you all for taking time to ponder upon my queries…
Boobka, interesting observation…
Padeye,
Yes most of my questions are about the enforcement aspect rather than the technical workings of the radar guns, as i had mentioned in my OP.
no i wasn’t looking for a camera crew… but the cameras used in the underground network are rather big and noticeable, i was looking for something like that… but i guess cctv and speed cams differ drastically in size then.
straightforward explanation there.
“Speed is a measure of distance divided by speed.” ?? is that what you really meant, or did u mean S=D/T ? but the rest of your answer makes it clear that i would still be clocked under 60mph. thanks.
Popup,
i thought the SDMB was free of Popups… but now we have you…
that’s what i thought, perhaps cams are not active all the time. but what i would specifically like to know is that : is it common that, assuming 50 people are clocked above the speed limit in say a one hour period, that not all 50 are fined by the cops because some were maybe not as fast as the others, even though they were all above the limit. Anyone know the policies governing these decisions ?
no i don’t have keyboard problems i just choose not to capitalize every I (and most other capital worthy words), because it saves me a tremendous amount per day in typing time, and cumulatively over a given day, gives me more time to…say… waste it instead on the SDMB
ok, so 3 and 4 are clear. but i’m looking for more info on 1 and 2(specific to london).
no i wasn’t looking for a camera crew… but the cameras used in the underground network are rather big and noticeable, i was looking for something like that… but i guess cctv and speed cams differ drastically in size then.
i just choose not to capitalize every I (and most other capital worthy words), because it saves me a tremendous amount per day in typing time, and cumulatively over a given day, gives me more time to…say… waste it instead on the SDMB