Safe Speed Forums

What a drama queen! You can comfortably travel at 20mph in third or fourth gear, you don't need to be in first or second to travel at 20mph.

By what mechanism? Going by the laws of physics and probability, this assertion cannot be true.

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

Really? What car do you drive then? At 20mph in 2nd gear my engine is running at 1000rpm - barely above tickover. I once tried 3rd gear at 20mph and immediately stalled.

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

By what mechanism?

Marie Taylor, TRL

THERE is a vast amount of evidence demonstrating the strong link between vehicle speed and road accidents. So why does material keep appearing in the media suggesting the effect is small?

In the 1990s a number of police forces conducted a limited trial of an experimental accident reporting system. The results were reported clearly in TRL report 323 but they have frequently been misquoted.

Speed increases the impact of many of the factors which contribute to accidents. For example, "aggressive driving" or "driving too closely" are both much worse at speed. Such factors were recorded in the system separately from speed but speed plays a big part in their effect on accidents. The system also allowed speed to be recorded in its own right. The total effect of speed on accidents is obviously the sum of both types of factor.

Misunderstandings in the press appear to have resulted in two ways. First, speed identified as a separate factor in its own right was present in 15 per cent of accidents, not the 7.3 per cent, or lower figures, that are often wrongly quoted. Secondly, the 15 per cent is only one part of the total effect of speed on accidents. When allowance is made for all of the other speed-dependent factors, the contribution is, we believe, much greater.

This means that speed is far more important in causing accidents and increasing their severity than the misquoted figures suggest. Importantly, other TRL studies have directly examined the relationship between speed and accidents.

Studies of individual drivers have examined how drivers’ speed choice affects their likelihood of accident involvement (TRL 421). Accident records of more than 10,000 drivers were related statistically to their observed speeding behaviour. These showed clearly that accident risk rises the faster a driver travels: at 25 per cent above the average speed, a driver is about six times as likely to have an accident as a driver travelling at the average speed.
Road-based studies looked at how speeds on a given road affect accidents occurring there (TRL 421 and 511). Several hundred thousand observations of vehicle speed on almost 300 roads of different types were related statistically to the numbers of accidents on those roads. These showed clearly that the faster the average speed of traffic on a given type of road, the more accidents there are. Injury accidents rise rapidly with average speed if all else remains constant.
Many ‘before and after’ studies of measures that slow traffic and result in substantially fewer accidents have also been reported. All these studies together provide extremely robust evidence of how speed affects accidents. They are large-scale studies, of real traffic on real roads, involving rigorous statistical analyses. The conclusions are unambiguous. Ten people die and 100 are seriously injured on our roads per day. Improvements in driver behaviour have the potential to cut these statistics dramatically. Reducing drivers’ speeds will play a vital part in this.

Summary of other TRL findings

Traffic calming schemes in 20mph zones have reduced injury accidents by more than half. TRL 215
Traffic calming schemes in villages have reduced injury accidents by about a quarter. TRL 452
On urban roads, injury accidents reduce by between 2 and 7 per cent per 1mph reduction in average speed. TRL 421
On rural single carriageway roads, injury accidents reduce by between 4 and 9 per cent per 1mph reduction in average speed. TRL 511
The biggest reductions in accidents will result from reducing the speed of the fastest drivers. TRL 421
Drivers who travel faster than average are more likely to be young males driving high mileages alone in company cars. TRL 440
TRL Limited (the Transport Research Laboratory) is the UK’s leading centre for international research and advice on land transport. Marie Taylor leads the laboratory’s programme of research on speed and accidents.

I wish you would use the quotey button.

it easy to use. Use the square [] with quote="steve"] .. whateve he said yadda yadaa yaddaa ... und close with [/quote]


You can play with it too

For example




You should watch You Tube.. It most enlightening.






Grauniad very much so. Other journalists do report the truth.. und that thanks to Paulie really





Speed cams are on MAIN roads.

A590/a591/a592 /mobile on A595/ A6/A66 or mobile on bridge over M6 are not residential roads.


A666 St Peter's Way not residential. Only deaths were suicide jumps from bridge when Mad Doc training. Yesterday . they had another one. Jazz was supposed to be visiting us but call in to pick up pals und late as result.

A666 Kearsley (always been a speed trap since the 60s per the locals)


A14 cams.. not residential. Incidents down to ground fogs und traffic volumes.


A2 cams.. not residential as such

A6 scams. A676 scams.. A34 scams M42 scams.. . these are not residential und if you go on line und look at all locations .. you find none on a residential road.

But



we are in danger in many areas of having our lovely replaced by cameras. Und cameras do not stop crime or anti-social behaviour either.


Lottery as well as not all housing has cam inside

But you still not told us how to curb the anti-social behaviour which some cyclists indulge in. (Und they would if in cars too... by the way. They the mindless thugs really)

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Nicht ganz im Lot!
Ich setze mich immer wieder in die Nesseln! Der Mad Doc ist mein Mann! Und ich benutzte seinen PC!

UND OUR SMILEYS? Smile ... und the the world smiles with you.
Smiley guy seen when you read
Fine me for Safe Speed
(& other good causes..)

Greatest love & Greatest Achievements Require Greatest Risk
But if you lose the driving plan - don't lose the COAST lesson.
Me?
Je ne regrette rien!

Yet you agree that roads policing has reduced, further?

I was originally talking about trafpol levels. Would you not agree that the camera policy made it worse?


Now those didn’t answer my questions did they!


There’s no evidence of ‘bias on selection’ either, that doesn’t stop it from being a real and significant reality.

Traffic has always been growing. Try again.


That was in response to your ‘arrogant’ comment. Try not to misrepresent me.


Why not and why not?
Are trafpol more effective at detecting all forms of dangerous driving? (as opposed to one form of technical infringement)
Do we need to remain with the £60 for genuine dangerous drivers?


I don’t know about that!!! although I accept you must be slightly ... warn out!

Audi A3 1.6 petrol, have also had a 2.0 TDI, no problems in that either.

The Jags are happy enough in third gear urban at 27 mph -ish. They very noisy though at 20 mph in first und it not do their engines that much good either.

The Moggie und the other toy boys beg for mercy. It why they used to tell you to get up the gears.

_________________
Nicht ganz im Lot!
Ich setze mich immer wieder in die Nesseln! Der Mad Doc ist mein Mann! Und ich benutzte seinen PC!

UND OUR SMILEYS? Smile ... und the the world smiles with you.
Smiley guy seen when you read
Fine me for Safe Speed
(& other good causes..)

Greatest love & Greatest Achievements Require Greatest Risk
But if you lose the driving plan - don't lose the COAST lesson.
Me?
Je ne regrette rien!

So, you can't actually drive these things at a sensible speed in a residential neighbourhood?

Personal experience both as as driver and a pedestrian, observing the increasingly stupid behaviour of other pedestrians over the years.




Differing levels of responsibility doesn't equate to a joint effort being utterly wrong - joint effort doesn't mean both sides must deliver an equal level of effort, merely that there should be SOME level of effort from both sides. Or do you think pedestrians have NO responsibility for their own safety?

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Chris

By respect do you mean obey? If that's the case count me out.

Barkstar

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The difference between intelligence and stupidity is that intelligence has limits.

SteveCharlton, you have not answered my question. If traffic-activated signs (advisory, shaming) can have a similar effect in my village to the Gatso (punative, secretive) in yours, why are you so in love with speed cameras?

10 years down the line we have a proper accident investigation reporting scheme. Care to remind us what that says?

Only when speed considered in isolation. The real world application of this is not nearly as straight forward.


Yeah, like their enormous mountain of paperwork!


It would be a non-sequitur to suggest that car impact protection is not getting safer based on that!


Proof of all sub claims please!

Traffic-activated signs can only be placed where the silly criteria for speed cameras are not fulfilled.


Winnett and Wheeler (2002) conclude that vehicle-activated signs appear to be very effective in reducing speeds because they can be operated at thresh-olds well below normal police enforcement levels and because they can be placed in road contexts where cameras would not be justified under the cur-rent criteria such as junctions on single carriageway roads with a 60mph speed limit.


Meadows (2003), in an evaluation of the speed awareness course run by Lancashire County Council, points to a positive impact of the course on drivers’ attitude to speed and to self-report measures of violating behaviour. It would appear that both education and engineering have a part to play in speed reduction. With any policy, it is always necessary to assess both the effectiveness andappropriateness of its application.




The final report includes an analysis of all the means avail-able to reduce speed on a variety of road types. On automated speed enforce-ment, it concludes that cameras reduce speeding but that the impact is limited in time and space and that the effect can be improved by installing a number of camera boxes along the road. The effectiveness of the digital SPECS system in Nottingham city, using digital cameras to enforce a speed limit across a sec-tion of road, bears out the truth of this conclusion. In conclusion, cameras have a place to play in a policy of speed management. Their effectiveness is likely to be site or area specific.



They will need to be ac-companied by educational and advertising campaigns to ensure that the bene-fits of cameras are made clear to all road users.



The evidence from the first two years of the pilot projects is that they are successful in reducing deaths and injuries where they are installed. To suggest otherwise would appear to flyin the face of both research and reality. Parliamentary Advisory Council for Transport Safety PACTS Research Briefing on Speed.


Once again, traffic-activated, cameras and traf pol are not all mutually exclusive, I say bring on more of all three.

I asked you a very specific question. Well, I suppose this is the season

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

I would say that Wildy has the ability to drive at an appropiate speed in any conditions, however she has no wish to cause the engine to work harder than it has to by making it labour in too high a gear at too low a road speed.

Of course it isn't just about making the engine work harder, if you want to drive around at 20mph in 3rd or 4th then the unneccessary labour you are putting on the engine will cause it to fail prematurely.

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

Only when speed considered in isolation. The real world application of this is not nearly as straight forward.

Speed is not considered in isolation. Read the report. Speed wasn't the focus, it emerged as the single prevailing factor.




Yeah, like their enormous mountain of paperwork!

Lobby to reduce paperwork then- that's a singularly absurd excuse.

[quote="SteveCharlton"]Safer cars having an impact?


It would be a non-sequitur to suggest that car impact protection is not getting safer based on that!

I agree, that's why i made no such assertion, I said that motorbike deaths rose and skewed the figures.




Proof of all sub claims please!



In the links provided.

Speed Cameras the Twisted Truth

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Useless laws weaken necessary laws.

How dangerous is speed?


The ABD'S lonely 'factoid' and the real world.



The Association of British Drivers (ABD) likes to cite a Transport Research Laboratory (TRL) report as a source for the true contribution of speed to road crashes and casualties. ABD members use the TRL report to contradict the 'mainstream' figure indicating that at least one-third of crashes are speed-related.


According to the ABD, the TRL report proves that the true figure is under 5%. This is the only source of such a low figure. The ABD and a few motor lobby journalists are the only people to use it, generally to support the argument that "it is not speed but bad driving that is dangerous". The ABD especially likes to use the figure in letters to local papers where highway authorities are implementing speed control measures in response to deaths and serious injuries or local demands for safer communities. (Their preferred technique is for one or two writers to flood papers with pseudonymously penned letters to make it appear they have widespread public support.)

The Slower Speeds Initiative wrote to the Transport Research Laboratory concerning the ABD's use of the study. The TRL referred us to reports on speed. This is because the TRL study cited by the ABD, TRL Report 323, concerns "

A new system for recording contributory factors in road accidents".


TRL 323 is not a study of crash causation. It is a study of how to collect data. It was not designed to draw statistically reliable conclusions about the causes of road crashes. The accidents included in the three month study were not a statistically representative sample of all accidents. There is no basis for using the study to generalise about the speed-crash relationship.

The very low figure quoted by the ABD comes from a table which showed pairings of factors: In 4.04% of crashes recorded in the study, the person filling in the form paired 'excessive speed' (nowhere defined) with 'loss of control of vehicle'. 4.04% is only a subset of all speed related crashes recorded in the study.


This use of statistics has been described by a professional statistician as "extremely naughty" and by the Department of the Environment, Transport and the Regions as "mischievous". DETR go on to say "it is interesting that none of the many other TRL reports on speed and accident risk have been mentioned by those using this report as the basis for their argument."

The TRL 323 methodology for recording contributory factors simply does not ask the questions which would reveal the inherent dangers of speed:

Would the factor still have been present if the driver, and/or all the other drivers involved, had been driving more slowly?
IF YES, Would the factor still have resulted in a crash?
IF YES, Would the crash still have been so severe?

It is obvious to almost everyone (with the exception of libertarian motorists with a soap box to drive) that higher speeds reduce the amount of time any driver has to respond to the unexpected and that higher speeds increase the force of any impact. The importance of reduced speeds to crash prevention and reducing crash severity is no mystery. In fact, the TRL study beloved of the ABD and its fellow-travellers, indirectly acknowledges the overriding importance of speed:

"Virtually the only factor that road accidents have in common is that all would have been avoided if those involved had known with certainty, a few seconds in advance, that an accident was about the occur."

Lower speeds provide those few extra seconds.

Among the TRL reports the ABD does not like to cite is TRL 421, "The effects of drivers' speed on the frequency of road accidents" published in March 2000. Unlike TRL 323, this study was designed to discover the speed-crash relationship.

The authors looked at 300 sections of road, made 2 million observations of speed and got 10,000 drivers to complete questionnaires. They found that

the faster the traffic moves on average, the more crashes there are (and crash frequency increases approximately with the square of average traffic speed)
the larger the spread of speeds around the average, the more crashes there are
Significantly for the ABDs argument, and for the rest of us, they also found that:

drivers who choose speeds above the average on some roads tend also to do so on all roads
higher speed drivers are associated with a significantly greater crash involvement than are slower drivers
For these reasons they conclude that the speed of the fastest drivers (those travelling faster than the average for the road) should be reduced. The study confirmed what is described as a 'robust general rule' relating crash reductions to speed reductions: for every I mph reduction average speed, crashes are reduced by between 2-7%. More specifically, the crash reduction figure is around

6% for urban roads with low average speeds
4% for medium speed urban roads and lower speed rural main roads
3% for higher speed urban roads and rural main roads
To put the dangerousness of speed into perspective, how many drivers care about or would notice a 2mph reduction in their average speed? Yet, averaged across the entire road network, a mere 2mph reduction in average speeds would prevent more than 200 deaths and 3,500 serious casualties a year. The authors of TRL 421 suggest that this target (about a sixth of the overall speed related casualty figure) is a 'reasonable minimum' to aim for. More importantly they use it to show "the sensitivity of accident numbers to a small change in average speed". In other words, speeds that might not seem excessive. Speeds that TRL323's methodology wouldn't even record. Thanks to Stephen Plowden, Rosamund Weatherall and DETR