Speed cameras are fixed or mobile photographic cameras rigged to a speed measuring device (In other words, its got two parts: The part that measures your speed, and the part that takes your photo.) They are deployed by the police in order to automate catching of speeding drivers. Whether they succeed in lowering speeding in general is matter up for much debate, but no one can deny that when a fixed speed camera is put in, drivers generally don't speed past it.
There are many different types of speed cameras, each with their own method of operation. However we can split them up into two general categories; fixed and mobile cameras.
Fixed cameras are as they sound, fixed in one location. These are almost always mounted on a pole of some sort. They are usually rectangular in shape, and have two holes in the business end; one for the camera and the other for the flash. They come in many different colours, in the UK they are usually grey and in New Zealand, cream. Sometimes they can be camouflaged so they can't be seen as easily. In New Zealand its common to find then just in front of a tree that obscures them from view till you pass (and they take a photo of the rear of your vehicle).
Fixed cameras generally either work with a KU band radar or sensors in the road to measure your speed. Obviously the radar devices can be detected with radar detectors, and the in-road sensors can't. Contra to popular belief, some speed cameras can detect cars in seperate lanes on freeways and motorways, they can also detect which car is speeding when there are multiple cars side-by-side.
Radar based speed cameras work much the same way as standard point and shoot cop radar guns. The radar is pointed at a particular location in the road, and when a speeding vehicle is detected, the camera takes a photo. The camera will usually overlay details such as time of day, date, measured speed, trip speed (the speed at which the camera will take the photo), and other information about the site. Some radar based speed cameras can detect the size of the vehicle passing, thus tripping at a lower speed for trucks and busses (who may have a lower speed-limit in the area).
Sensor based speed cameras work by having sensors embedded in the road in front of the camera. These sensors detect your speed in much the same way as you may have done in physics in school. The sensors measure how long it takes to go between a known distance, then calculate velocity based on that. These sensors can be a varity of different devices from rubber hoses to magnetic sensors. Since they are entirely passive, there is no way to detect them (other than the tell-tale flash as the camera busts you).
Fixed location cameras are less likely to catch offenders since their location can become known very quickly. The police attempt to offset this by having more speed camera boxes than actual cameras, and move the cameras around regularly. In New Zealand, unlike in the UK, the inactive camera boxes don't flash when you speed past. In the UK only the actual camera (the most expensive part) is moved around, so the "empty" boxes still flash and pretend to have caught you.
In New Zealand, the speed camera of choice in fixed locations is the AutoPatrol SP-200 pole mounted camera. This system works with in-road sensors, so you can only spot them visually. In other locations around the world many different other systems are used. The British use the commonly use the GATSO systems.
Mobile cameras are usually mounted inside vehicles, but recently they have also been mounted on trailers (using the same technology as fixed cameras). Mobile cameras obviously can not rely on in-road sensors, so they are almost always some kind of radar type device.
In some places around the world, mobile speed cameras can only be used in designated areas. In New Zealand, when this was in effect, someone painted out the "camera" of the "speed
camera area" sign and all tickets issued in that area that day were void.
The cameras are usually mounted in the back of station wagons or vans due to the size of the equipment. Some cameras setups can be used through the glass of a vehicle, others require the rear door of the vehicle to be open. The move is towards the systems that work through the glass since the rear door being open is a dead give-away to the presence of a camera. The systems that work through the glass still require the flash unit to be mounted outside of the glass (due to reflection), so the flash units can be mounted on the tow-bar of the vehicle.
Mobile speed cameras work in much the same way as the radar based fixed cameras and the normal point and shot radar gun cops use.
Laws and regulations
These change as much with time as with location as speed cameras are accepted by the local population. Initially in New Zealand, the speed cameras were only to be used in designated areas and were not allowed to be hidden. They also only ticketed the top 10% of speeders that day. This has changed, the quote from the New Zealand police is "the gloves are off". Speed cameras can be hidden, used anywhere, and the police will ticket as many people as they like (especially during the holiday period).
Interestingly enough, initially the New Zealand police did not like it when drivers would warn other drivers of speed cameras and speed traps by flashing their lights. However in recent times the police have said they are happy with this practice, stating that they are for anything that reduces speeding. In a small town in New Zealand, the locals put up a fake speed camera box on a busy, often sped road. Some complaints were made to the police, however the police simply congratulated the anonymous persons who put the box up, again happy with anything that reduces speeding.
In New Zealand, a speed camera ticket is a charge against a vehicle, not a person, so the registered owner of the vehicle gets the ticket. This is important when it comes to burden of proof. If the charge were against a person, then the police would have to prove that it was indeed you driving the car, but as it is against the vehicle, they can easily prove the vehicle was indeed in violation. Its the same as a parking ticket. This also comes in to effect with demerit points on licenses, A speeding ticket (given by a cop who pulls you over) can incur demerit points on your license (too many points = loose license), however speed camera tickers don't incur demerit points. I think this is where some of the problems in the UK over speed cameras come from.
In the UK there has been much controversy with speed cameras in recent times, and I am not going to pretend to know many details about it. I encourage any noders with knowledge on this to do a WU about it below.
- http://www.speed-trap.co.uk - UK related information on speed cameras, including detailed information on how various speed cameras/speed sensors work.
- http://www.geocities.com/SiliconValley/8443/Other_sp-200.html - Information on New Zealand speed cameras.
- http://www.police.govt.nz/ - New Zealand Police website.
- Some information on speed cameras produced by the Australian New South Wales government.
Some of the information above is from personal experience and talking with various law enforcement personnel.
As with all articles regarding law enforcement techniques and equipement, the best way to avoid being caught is not to break the law in the first place. Don't speed, there is no such thing as safe speeding.