Safe Speed Forums

I have introduced this topic in order to explore the case for speed cameras, and to answer the question of how speed cameras are supposed to reduce accidents and/or casualties.
This is intended to be an objective debate, ie the central question is: by what mechanism can speed cameras have the desired effect?

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

For the none speeder, the effect is to make them frightened they might accidentally be caught, so they make sure by looking constantly, and checking as they pass a camera... just in case! They usually pass a 40 mph camera at 25 - 30 mph - frustrating the none nervous drivers behind, a few of whom become determined to pass as soon as possible.

For the driver who speeds, looks CONSTANTLY for the camera - he/she is not concerned with their speed. When they spot the camera, they brake hard to ensure they are well below the posted speed as they pass, then it's up to the speed they carried before.

Within a few yards of the cameras, speeds will fall slightly. Overall, the drop is minute, and does not persist, except in a very few drivers.
Those the cameras are aimed at (purportedly) are the least likely to carry on at a slower speed, thus ensuring a steady income!

So the mechanism is fear of getting caught - not respect for the law, or the posted limits. And excepting cameras operated by a constable at the roadside, the cameras NEVER stop an offence from continuing!

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

I tried to raise this topic some time ago in a thread entitled How are speed cameras meant to work?

And no camera supporter has ever satisfactorily explained the mechanism to me. The first question is whether the claimed effect is primarily general or site-specific.

It's worth repeating what I originally said:

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

Even the "camera's by constable" fail to apprehend the stolen vehicle, the vehicle (sorry, driver) without appropiate paperwork in force, the pissed up driver, yada, yada, yada....

All they are interested in is the £60 (which they won't be getting from any of the above anyway).

20 odd years ago, it was nigh on impossible to undertake a journey without coming across a copper (bent or otherwise).....now it is impossible to spot a copper no matter how long your journey is.

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What makes you think I'm drunk officer, have I got a fat bird with me?

They do only if the offender is stopped at the time of the offence.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

That is just the problem though Peter, as long as they have satisfied themselves they have photographed you, they aren't worried about actually stopping you and doing a proper check.

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What makes you think I'm drunk officer, have I got a fat bird with me?

Guys

No offence, but this is already drifting off-topic.
It's meant to be a discussion of the underlying mechanism by which cameras are supposed to achieve their stated goal of reducing accidents and/or casualties.
For argument's sake, if they're supposed to work by slowing drivers down, then we have to look at how slowing drivers down is supposed to prevent accidents.

Anyway, Happy New Year to all

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

the case for cameras: money for the coppers

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2 fast, 2 furious!

Well Pete, I hope I summed up my take in the final line....

The whole thing works better when the fear of getting caught is obvious AND IMMEDIATE.
In France, when the police operate a radar trap, they choose a bit of road, and film the offending drivers, then at the first safe place, ALL the offenders are pulled over by another police car/motorbike, and made to WAIT while they are each processed. On a busy day, it might be twenty to forty minutes before the policeman gets to your window to take down your particulars.
During that time, you go NOWHERE, and are seen by other drivers passing.

It is just SO effective as a deterent, and from the times I have seen it in Brittany, the sites are always ones where the risk of an accident is heightened by speeding over the limit.
Of course, while on site, other offences are monitored too - and some like no insurance or control technique carry the risk of having the vehicle siezed - again, at the road side.

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

Who left the door open?

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

The case for cameras in summary:

1) There was a belief that driver behaviour would change across the entire road network and less speeding would mean less crashes 'caused by speeding'. However, drivers speeding behaviour, at least as reported officially, remains unchanged.

2) There is a belief that reducing the average speed of traffic (at camera sites and elsewhere) will reduce the risk of crashes. However, the science that purports to support this notion is amongst the most twisted and contrived that I have ever read.

3) The was a suggestion that traffic police, freed from the duty to 'catch speeders', could be employed doing other useful safety work on the road network. However we've seen the numbers of traffic police and the availability of traffic Police decline markedly.

4) I think there may have been a belief that cameras would force a more 'law abiding mindset' on drivers, with a greater amount of visible law enforcement acting as the agent. However, the opposite has been true - respect for the law has been undermined.

Digging a little deeper into the beliefs associated with 'speed kills' policy we find key false assumptions. These are discussed on the following Safe Speed page: http://www.safespeed.org.uk/conspiracy.html

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

There is also the other reason: most drivers exceed the limit so if you stick a camera at a blackspot where drivers weren't paying attention, all things being equal an accident will be less likely or less severe as they will have more time to react as they are travelling more slowly. If risk homeostasis works then drivers will just look less far ahead because they are travelling at the lower speed hence the benefit disappears.

By what mechanism?

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

The case for cameras are based on a lot of false assumptions. One of them is that speed in excess of the speed limit is the the primary cause of a majority of accidents. The next assumption was that by erecting thousands of these boxes people would therefore abide by the speed limit, but maintain the exact same level of concentration as before. Then you get into the logical physics argument that obviously proves that a a car will be able to stop in a shorter distance if it is traveling slower. The problem with that is that it assumes everything else, such as concentration, will remain constant. It doesn't. That's before you even begin to look at all the negative aspects such as drivers diverting attention away from the road to looking for cameras and checking speed obsessively.

That's one of the very big red herrings.
Yes, a car will be able to stop in a shorter distance at a lower speed.
But that's irrelevant - for the simple physical reason that if the car was doing a different speed (higher or lower) then it cannot be at the same place at the same time.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

I don't buy that argument Pete. It's true on the 'micro' level of course - a single vehicle coupled with a single incident.

But it just doesn't scale. If you look at an average vehicle and an average incident the argument is false.

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

Is that because it's just as likely that by going slower the vehicle would not come in conflict with another as if it was going faster, and therefore being in advance of what would have been an accident? Or am I getting confused?

Sorry, is what because? I can't figure out what you're replying to.

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

I was explaining things on a 'micro' level - if the speed is different then the same collision cannot occur. However it's also true to say that a different collision may occur - that same car might collide with a different hazard, or another car might collide with the same hazard - and here we start scaling up to averages for the population.
But to stay at the micro level for the time being, the central plank on which mainstream research rests (Kloeden et al as an example) is the assumption that the point in time and space at which the driver becomes aware of the need to brake is the same regardless of speed, and therefore:

a)the average risk of collision is proportional to the total stopping distance (the square of speed plus reaction distance),
b)the lower the pre-incident speed the lower the impact speed, should the collision still take place, and
c)the driver has more time to react if the pre-incident speed is lower.

Removing that fundamental flaw, it can be shown that:

a)the average risk of collision is proportional to the pre-incident exposure time (reaction time plus half the braking time),
b)no link exists between pre-incident speed and impact speed (although, obviously, the pre-incident speed does determine the maximum possible impact speed), and
c)the amount of time the driver has to react is independent of speed - although it's true to say that the time required to react is dependent on speed, but this only amounts to around a quarter of a second for every 10mph. Whether or not the driver has the required time available is decided by random factors (time, place).

When this is scaled up to the average population, a very different picture emerges than what mainstream research indicates.
It now becomes clear that, on average, that although speed does have some effect on collision risk, its effect is small compared to the effects of reaction time, inattention etc. And that's before psychological effects are taken into account.
Mainstream research also fails to take into account the fact that, by and large, drivers tend to modify their speed (and attention levels) according to the perceived level of hazard - ie they slow down for hazards as well as sharpening their wits. This fact almost entirely removes speed as a factor in the average risk of collision.

One other point: whichever model one chooses, the overall risk is proportional to the number of hazards - double the number of hazards and you double the risk of collision, independently of other factors.
Which is why the current misguided policy of increasing hazards in order to make drivers slow down is so (literally) fatally flawed.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

Pete - Ilike the argument you have put forward, and the assertions you make appear reasonable - BUT, playing devils advocate, do you have evidence or citable research to back up the assertions I have emboldened in the quote above?