Take the 2-minute tour ×
User Experience Stack Exchange is a question and answer site for user experience researchers and experts. It's 100% free, no registration required.

In the UK, speed cameras are usually accompanied by white striped lines on the road. I have always assumed that was a visual reminder to the motorist to "watch your speed- it's about to be checked".

enter image description here

However speed cameras can only detect speeds of traffic moving away from them. So on a two-lane road with traffic going both ways, it will only ever detect speeds from one of the lanes. So the white stripes seem superfluous.

What is the psychology behind putting these lines on the road, even when the camera is not pointing at them?

share|improve this question
    
From a driving point of view it does also serve the purpose of warning you that there are speed cameras (ie on motorway gantries - where they are not obvious) and they are where you should be looking (the road) rather than where the actual warning signs are (the edges of the gantries) –  PhillipW Sep 25 '13 at 19:30
    
I wondered whether it was simply to put a little bit of doubt in the motorist's mind- "Am I sure it won't go off when I speed through it in this direction. Maybe better not risk it." –  Urbycoz Sep 26 '13 at 9:09
    
"The white stripes 'seem' superfluous" There is your error. This is not a UX question. –  JamesRyan Sep 26 '13 at 10:09
1  
@JamesRyan A question involving modifiying the design of petrol forecourts to make them more efficient for the user, and thus more usable, seems like a perfectly on topic question to me. –  Racheet Sep 27 '13 at 12:51
1  
To me a petrol forecourt is an interface, meanwhile a chemical reaction clearly isn't. There's no human, and proper design isn't going to improve anythings usability. –  Racheet Sep 27 '13 at 13:01
show 7 more comments

2 Answers

up vote 9 down vote accepted

Early speed camera designs made use of radar beams only. These have been shown to provide reading with high errors, sometimes ridiculous ones. In some countries, like Israel, this has resulted in a legal turmoil, where at some point (with the help of specialised legal firms) not a single offender was convicted in court. This has prompt a revision to the law and the calibration procedure of these cameras. But the problem was not quite solved.

To combat the issue, manufacturers have added a 2-frame camera (usually with 0.5s time interval) to the already existing radar system. The white lines on the road are used as mere rulers. Since the car will hide the ruler on the lane it is driving on, there's also a ruler on the adjacent lane. It just happens that if there's only one lane per direction, the adjacent lane will be on the opposite direction (but same direction if there're two lanes in each direction).

A photo of the speed camera on kingsland road

It seems that in the UK and Australia, a conviction is made if the error between the photo analysis and the radar reading is within a 10% margin.

You can read much more about this here.

share|improve this answer
1  
They also do this with large think lines, so that planes can see from the sky, that if you go from line A to line B within X amount of time, then you're going Y speed. Lots of places around here have signs that the speed limit is enforced by air patrol. –  Mike Mersereau Sep 25 '13 at 17:31
add comment

Are you sure it's purely psychological and not technical ?
With 2 photos taken at determined interval you could prove/verify whenever you want the speed of the vehicles.

Maybe it's only psychological, maybe it's technical, maybe it's forward thinking. There could be an upgrade someday.

In France we have front and back speed camera, single and multiple lane. The last generation can even detect car vs large goods vehicle. So you could not trust speed camera to only detect some car in specific condition in the future.

share|improve this answer
    
No, I'm not sure whether it's psychological. I just couldn't think of a technical reason- they seem unnecessary. –  Urbycoz Sep 26 '13 at 7:59
    
Seems unlikely to be "forward thinking". How hard is it to draw lines on the road? –  Urbycoz Sep 26 '13 at 7:59
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.