Speed Limits

COPY OF C. COOKE OBJECTION TO A5 SPEED REDUCTION PROPOSALS

To:
Highways Agency
Traffic Operation Orders Team
C4 Broadway,
Broad Street
Birmingham
B15 1BL

Ref: HA 28/2/148

Dear Sirs

A5 Trunk Road (M42 Junction to Grendon, Warks) (40mph and 50 MPH speed limit)
Order 200

I wish to register my objection to the above order.

I write as a local person living close to the M42/A5 who has driven along this road for very many years - and still do so regularly having friends, family and business interests out that way. I also write as a Local Councillor with many people in my ward using this road on a daily basis.

First I would question the Secretary of State's ONLY given reason for these reductions in speed limits. He states merely that there had been 55 Personal Injury accidents from 1st July 1999 to 30th June 2004 - a five year period that's 11 per year. I don't have the actual accident statistics for that stretch of road - and there is no way I'm going to be able to get them before the consultation period is over. But I do have the accident statistics for various other stretches of road around nearby Tamworth where I live. An almost three year period (02/02 - 12/04) saw accident figures on the Pennine Way (B5080) at 35 - that is nearer to twelve per year. Yet this Pennine Way is a straight stretch of road with speed cameras, deliberately narrowed lanes and speed limits of 40mph for half its mere 1¼ mile length and 30mph for the rest. That equates to 61 personal injury accidents over a five year period. Compare that to this stretch of the A5 that you intend to put these limits on. First it is well over double the length of the Pennine Way and with at least twice as much (and the rest!) more traffic on it than the Pennine Way. And yet this 3 mile stretch of the A5 only produces a Personal Injury Accident rate of 55 - far less than a comparative rate for the B5080. Please bear that in mind and, before I am accused of being complacent, please read on.

Second I would question the type of accidents involved on the A5. There is no evidence to suggest that they were speed related accidents nor that they happened at regular intervals along this road, nor what else there causes were judged to be. There is no evidence the Secretary of State offers to back up believing that these accidents could have been prevented by having a lower speed limit. They have not been analysed by him.

Third I recall from some years ago that on the Dordon to the Grendon Island stretch an accident that I believe resulted in a death was caused by a SLOW moving vehicle. No suggestion that any speed limit was being broken.

Fourth - I mention the third fact because after - and probably because of - that accident the Highways authorities did a great deal of work on that stretch of the road. They made it single carriage way all along, they put in regular middle-of-the-road traffic islands. I believe this highway engineering itself has been useful. But what is obvious is that the figures the Secretary of State has used makes no attempt whatsoever to compare the Personal Injury Accident statistics before and after this road engineering. I would suggest that this road engineering itself has significantly decreased the risk of accidents on this stretch of road. So the figure of 55 over the period used is even lower now. These "before and after" figures should have been compared, and used by the Secretary of State, before any attempt is made to reduce limits further. The Secretary of State should allow more time for a comparison to be made if the figures are not yet available for comparison for a full three year period.

Fifth. I know this three mile stretch of road very well. From the Dordon to the Grendon Island it is as straight as a die (in fact the whole road is - that's the way the Romans built it!). Not only that but visibility either side of the road is wide and excellent. There are large tracts that have a lane-width side road to it and - equally important - at least a lanes-width painted out in the middle of the road from oncoming traffic. Effectively it is almost as much duel carriageway as the M42 to Dordon Island stretch.

Sixth. There is no evidence at all that the Secretary of State has done the traffic assessment required by Government guidance before these speed limits were ordered - nor how that traffic assessment significantly differed to the previous traffic assessments when it was considered that the previous speed limits were the correct ones. What has changed? I reproduce here the guidance from Department of Transport Circular, Roads 1/93
--------------------------------------------------------------
50 and 60mph Speed Limit

Lightly built up. Some frontage development.

Rural roads. Development not essential but maybe cafes or filling stations or other features which attract traffic, e.g. parks and sports grounds.

Suburban roads or high standard roads on the outskirts of urban areas.

Roads with restricted visibility or junctions or, where dual, gaps in the central reservation. By-passes which have become subject to some development.

Few pedestrians (or full provision for crossing by means of subways or bridges). Few pedal cyclists (or road provided with cycle tracks)
------------------------------------------------------------------------

That criteria set out here suits the part of the A5 from Dordon to past Grendon for which you are proposing your 40mph limit. There is a footbridge at Dordon for the few pedestrians that there are around that cross the road. There are some junctions but always with good visibility. There are few cyclists - and lanes that can be used as cycle paths. This stretch of the A5 is clearly a high standard road. And I am only asking that this speed limit remains at 50 - the lower limit for these criteria.

Seventh. Now I will freely admit that often the traffic along here already travels less than the 50mph limit - usually because of heavy vehicles. I see no sign of impatience by drivers. However, reduce that limit to only 40 and there will be drivers - perhaps those afraid of more points on their licences - going excessively slowly to provide a "safe" margin of error. I attach a Dept of Transport report circular, Roads 1/80 that shows the effects of such a reduction will most likely cause more accidents. I go back to what I said earlier - that accident figures - for the length of road and volume of traffic - are already low for this stretch of road - and most likely unrelated to speeds over 40mph. If you lower the limit the effect will very likely cause an increase in accidents.

I am also concerned that if you reduce the speed limits on this road you will increase congestion and therefore the amount of traffic taking the "back" way along the B5000 a road that runs somewhat parallel to the A5 and for the most part has no speed restrictions on - although it is clearly not a main road like the A5 and should not be taking that sort of traffic. This may increase accidents on the B5000. It is better to keep the traffic on the main A5.

Therefore I strongly urge you to keep the whole length of the proposed A5 stretch of road to 50mph.

One further point. On the details laid out in the library, in words you imply the 50mph limit will be set "from the M42 island" itself. Yet on the diagram it quite clearly illustrates that from the island for about a quarter of a mile towards Dordon the national speed limit will apply. I would support the diagram version. Which version are you proposing?

I would also support instead a 60mph limit for the remainder of your proposed 50mph to just past the Ambulance station. I would suggest that it only became a temporary 50mph limit because there were various road works taking place. Now those road works are gone this is a highly developed, duel carriageway with very little by way of development either side. But I am less opposed to this remaining at 50 than I am to the reduction of the rest of this 3 mile section of A5 road limited down to 40mph. I (and I'm sure many others) will suspect that the reduction must just be merely a device to fill the coffers of the police and camera partnerships.

Whilst I am not aware of any call from members of the public to have these limits reduced I do feel that if there are members of the public who have asked to have the limits reduced then they have done so as they have been conditioned to the assumption that it will reduce accidents as they are so often told. I doubt if those people would support reduction of speed limits if they believed it could actually make the accident rate worse - as the enclosed Dept. of Transport paper suggests. I believe they - like I - would instead ask for proper policing of our roads to take out those drivers that drive inappropriately for the conditions - which may - or may not - be above any set speed limit.

Could you please advise me of receipt of this objection and what the process is now through which it will be formally decided? Will it be through a Local Council or is this a decision for the Highways Authority or Secretary of State himself? In other words will it go through a formal democratic appraisal by elected representatives?

Thank you

Yours sincerely

Cllr. Chris Cooke

enc. - 2pp Annexe E to Dept of Transport Circular, Roads 1/80

ANNEX E TO DEPARTMENT OF TRANSPORT CIRCULAR ROADS 1/80

THE EFFECT OF ALTERING LEVELS OF SPEED LIMITS: SUMMARY OF EXPERIENCE

It is a common but mistaken belief that drivers allow themselves a set margin over the prevailing speed limit, and that if a limit is raised by 10 mph, they will travel 10 mph faster. In fact, an increase in an unrealistic speed limit rarely brings an increase in traffic speeds. ("Unrealistic" is here used to mean "substantially below the 85 percentile speed"). It is much more likely that there will be no change, or even a fall. It seems that drivers relieved of the frustrations of too low a limit rarely abuse the higher one. Indeed it is not unusual for the accident rate to fall when a poorly-observed limit is raised. This may mean that reduced frustration leads to changes in driving behaviour conducive to accident reduction.

The evidence for asserting that speeds and accidents do not increase in proportion to an increase in speed limit comes from studies made before and after unrealistic local limits have been raised. Some of the main evidence is summarised in paragraphs 3-9 below.

In 1960, a Departmental Road Safety Committee reporting on the results of the experimental introduction of 40 mph speed limits in the London area concluded that the raising of the limit had resulted in no appreciable change in speeds, while the accident rate remained substantially the same. The committee considered that the higher limit had achieved its purpose of removing unjustifiably low speed limits, and encouraging a proper standard of enforcement.

A before and after study carried out at 20 locations through Kent, where the limit had been raised from 30 mph to 40 mph, showed a fall in speed, or no change, in 80% of the measurements taken, and a small increase in the others. The total number of accidents fell by almost 20%.

In 1973 the Metropolitan Police produced the results of a study on six sections of trunk road where — in accordance with the Department's criteria — speed limits had been raised from 40 to 50 mph, or from 30 mph to 40 mph. At four locations the 85 percentile went up by less than 2 mph and at two locations it went down. Allowing for a general decrease in accidents, the reduction in the number of accidents at these places was 15%.

When the speed limit in Park Lane, London W1, was increased from 30 mph to 40 mph in 1970, the 85 percentile speed fell from 43.6 mph (measured in 1970) to 39.2 mph (measured in 1974).

In 1974, the Midland Road Safety Unit reported the results of a study of a large number of speed limit changes from 30 mph to 40 mph. Their conclusion that there had been no significant increase in either speeds or accidents was in line with the conclusions from a similar exercise for cases in other parts of the country carried out within the Department.

The Department has recently conducted a survey of the effects of changing the levels of speed limits in various parts of the country. The results indicate that raising speed limits has little effect either on the speeds of vehicles or the rates of accidents.

The following examples of local speed limit changes from 30 mph to 40 mph illustrate this point.

85th Percentile Speed Accident Rate

County Road Before After Before After

Cheshire A41 44 43 1.06 0.6

Lancashire B5253 43 37 0.78 0.85

West Yorkshire A58 40/43 47/52 1.45 0.65

Warwickshire A34 42/42 43/43 0.5 0.65

Warwickshire B4453 42/44 43/43 3.2 1

Surrey 40/42

47/40

41/41

45/37

The table above shows that, in the one instance in which speeds rose, the accident rate went down.

With the removal of the energy conservation speed limits in June 1977, the national speed limit went up from 50 to 60 mph on single carriageway roads and from 60 to 70 mph on dual carriageway roads. This afforded an ideal opportunity to judge if traffic responds to national speed limit changes in the same way as it does to local changes. A survey of speeds at 49 points throughout the country made in July 1977, compared with a similar survey in July 1976, showed that for cars and motorcycles with a headway of at least 5 seconds there was no change in the mean speed on single carriageway roads and a 1 mph on single carriageway roads and 2 mph on dual carriageway roads (sic). An analysis of national accident rates in the months following the changes shows no evidence that raising the limits caused any increase in the number of accidents.

2ND REPLY

Attn. Mr Geoffrey Bevan
Highways Agency,
Traffic Operation Orders Team
C5
5Broadway,
Broad Street
Birmingham
B15 1BL

Your Ref: HA 28/13/2 PT1

Dear Mr Bevan

A5 Trunk Road (M42 Junction to Grendon, Warks) (40mph and 50 MPH speed limit) Order 200

Thank you for your letter of 10th July replying to my email. I am grateful for you replying using the same numbering system which does make things a lot easier to reference.

It does seem to me that in quite a few cases your answers do not meet the substance of each point made. Again using the numbered system.

1. The main point was that the Highways Agency has deliberately engineered the road in order to reduce speed - rather than for any other reason of road safety - purely to allow you to reach an 85% percentile that you then insist must mean a reduction in the set speed limits!! You say it was your "intention to change driver behaviour". But by that phrase you surely can only mean one thing - to reduce driver speed? You have therefore pre-determined that speed is the "problem" - although nobody complained of any problem did they? And because drivers would not slow down enough on this very safe section of road - you engineered in various factors that did nothing more than slow drivers down!! I still cannot believe you did that!

2. I'm glad you agree speed limits can also be raised to reduce accidents - although I am obviously not asking for these particular limits to be raised. But you cannot have undertaken "very detailed accident analysis" including the recent changes because these would have to be done over a period of at least three years (although five years now seems to be the standard). Where is the evidence of these detailed accident analysis? Can you provide it for me? I would certainly be very interested to see whether the accidents (as far as can be statistically ascertained) have actually increased since your speed reduction road engineering installations. I would like to see what it is about this analysis that leads you to believe your reduced speed limit "proposals will have a positive impact on road safety". I fear the true impact will be a very different - and negative - sort of impact!

3. In this one the main point was that there are no pedestrians. You say there is no requirement to count pedestrians. You even say that slower speeds would encourage more pedestrians. That sounds dangerous to me on a road that has a constant traffic flow. The main point is that there is nothing that pedestrians would cross for - there is nothing on the other side of the road. So why encourage pedestrians by reducing set speed limits? And if there is nothing pedestrians would cross for why do Highways talk about "consultations with local residents" - incidentally another piece of evidence that remains frustratingly unavailable to me. The only place residents might cross, as your answer indicates, would be at one of the two islands - where the traffic is obviously very much slower than any proposed new speed limit. And there is a footbridge nearby on at least the Dordon island. I know Highways Dept. are supposed - by Government order - to put the interests of pedestrians before cars - but that surely means better pedestrian facilities, better pavements, better walkways etc. Roads, like it or not, are still for motor vehicles. The road is not a safe place for pedestrians. Highways should not be trying to encourage more pedestrian use of this national trunk road this way. That really will increase accident statistics!

4. Despite your web link - and me spending far to long looking - I can find no trace of consultations with any residents along this A5 stretch of road. Perhaps you can provide a more specific link or even the actual information? It doesn't seem a lot to ask.
I am mildly curious as to what "enforcement" you say you work for with dangerous drivers who operate dangerous manoeuvres - often dangerous below any speed limit - or exceeding by considerable amounts properly set speed limits - out of the range of "enforcement" cameras of course. But that is not really relevant here.

5. So it wouldn't harm if I was supplied with the full details of your consultation with these residents - and their responses?

6. What you say for motorways is of course quite true. But your reference to a "detailed accident analysis" glosses over information that should be available to me without giving me reference as to where I can find this information. For instance where you claim a higher "slight casualty" rate - I immediately think - "and what of the seriously injured and killed rates?" I would imagine the higher "slight casualty rate" is due to the fact that this stretch of the A5 is safer than the A46, A38, and A45 (although these are huge roads to compare with??) and therefore - in much the same way as WW1 soldiers received more head injuries after being supplied with helmets .. the reason being that far fewer of them were being killed as a result!! But really - only 55 injuries over a five year period (how many accidents was that?). Quite a few of those injuries no doubt from multiple slight injuries in the same collision. This tells me that this is not a road that needs speed limit reductions. I honestly believe accident figures will worsen if you go ahead. Why don't you wait for at least a three year period after your road engineering works - and then see what "accident" comparisons can be made - and whether you still believe speed limits should be reduced.

7. A blinkered approach considering that Highways are rushing these new speed limits in ahead of the new guidelines - and without proper comparisons/analysis of road conditions and accidents since your road engineering has taken place.

8. We have to differ. I know (inappropriate) traffic already diverts from the A5 at peak times - when there is most certainly congestion - along the B5000 to the Amington and other Tamworth industrial estates. And there are NO traffic lights, NO roundabouts (until Tamworth) and even a NSL applying along a majority of the countrified route! (what route are you thinking of??).

I followed a lorry doing precisely this just after 5.00pm only last week. Yes - it struggled to get past Polesworth's narrower roads - and yes, I had to struggle behind it - but this happens now! Speed Limit reductions will certainly make for increased congestion at the A5 island nodes (and here I do feel I have to emphasise - at peak periods - that's the important point here). Some traffic will inevitable bleed towards the B5000

9. Of course it's a Roman Road - it's straight! That's how they built them in those days! And it's nice and clear on both sides. Surely you cannot be telling me that straight roads are the more dangerous type! And of course any trunk road will always take in an element of local traffic. But there is not - and never has been - any evidence at all to suggest that this has been any sort of problem on this road. If so where is this evidence?

Of course not all journeys are made by car, some are by bus, or lorry or bicycle or by foot. I think Highways believe Government is saying that pedestrian and bicycle priority means mixing them far more with cars. That's a sure recipe for far more accidents. I believe Government is saying give the cyclists and pedestrians better off road facilities. That's surely what government guidance is really about.

10. I have been aware of the accident recording practices of the police. I see no reason to question the figures as produced. Transport For London is one of these quirky groups infested with a whole range of anti-car interests and - unsurprisingly - not a single car driver group representative. The bus and train operators in this group particular have a vested interests in getting people out of there cars - and to clog up the roads (except for buses of course!) is a great way to do it. No - I'm sorry - TFL does not provide reliable, unbiased information. Does your guidance specifically require you to take account of it?

11. I just wish what you say here is true. But all the evidence points the other way. There is less policing on the roads. Your "partners" or not, I see remarkably little in the form of working together past the usual statutory consultations. Speed enforcement cameras undoubtedly would not exist if they could not provide a profit for the companies that run them - and some money for the Authorities too. And I remember the days when police patrolled the roads properly - and speeding a few miles an hour above any set speed limit was not by any means their main concern. Safe driving was the imperative.

12. Yes - you are absolutely right - statistics can be misleading. Yet you then tell me that you rely absolutely on the statistics you have obtained to implement your A5 speed limit proposals (notwithstanding that I still haven't seen these statistics - especially the accident analysis details). So the statistics you use are OK then - its just the statistics you don't use that are suspect?

I find your last paragraph-but-one a little chiding. Of course we all want to stop accidents - that's why I make this objection. You seem to think its because I feel people have a God given right to travel as fast as possible. Yet it is your overwhelming belief in the "fact" that if speeds can only be reduced then so will accidents that shines through almost every word. It is the sacred shibboleth that cannot be argued against. But I do argue against it - and very strongly - because I know

a) that it is just plain wrong - sensible speeds are those we feel most comfortable with, and

b) inappropriate lowering of speed limit will increase accidents - there's enough evidence over many years to prove this. Why do you think the rate hasn't reduced - as you say - from your 1994-1998 average baseline rate? After all you've been cutting speeds on thousands of roads across the country. Accident rates were falling for many years before the Government started obsessing with speed. Now they've stopped. Despite car and road engineering proving us with ever safer environments. Ask yourself what's going wrong. And,

c) I understand that every 1mph reduction of traffic speed across the UK will cost the UK economy about a billion pounds. Now that may be fine if Highways can show that it really has reduced accidents - but the evidence is stacking up that they haven't reduced have they? Although I do note you talk about accident reductions - you still admit that they are greater than in the mid 1990s - which seems a contradiction? So we are not talking about "inconveniencing somebody a fraction of a minute" - its actually more than a few minutes on the average drivers daily journey times for each 1mph reduction on journey time, but I won't quibble - "to save one life". It's quite clear that when we "explore" ways of reducing accidents we find that speed reductions such as the ones you propose may actually lose lives. Therefore it is not people who "value their time above the life of other people". That's an unfair and emotive statement. It is whether the speed limit reduction proposals will actually achieve the accident cuts you claim will happen. Whereas it is my position that you are more liable to increase accidents - and I believe I have shown the evidence of that - and have yet to see Highways to show otherwise.

In my more cynical moments I sometimes feel that all this messing about with our roads - the A5 and the M6 - is more designed to push traffic onto the toll road than for any other reason. You also still don't say who will take the final decision and whether I could make representations to that body.

You suggest a meeting - and I think that would be useful if you could bring along your papers and the statistical evidence which you have depended on and which I have asked for. I'm open to your suggestion of a time and place - although close by for a "site visit" may also be of use. I understand my submissions have been unusually detailed and I did not expect you to answer every point. Perhaps in conversation we could reach an understanding?

Thank you

Yours sincerely

Cllr Chris Cooke
33 Camhouses
Tamworth
Staffs.
B77 4HJ
Tel 01827 735900

COPY OF OBJECTION BY PAUL BIGGS

ASSOCIATION OF BRITISH DRIVERS (STAFFS) TO A5 SPEED LIMIT REDUCTIONS

Objection to speed limit reduction proposals:

HA 28/2/148 - The A5 Trunk Road (M42 Junction 10 to Grendon, Warwickshire)

(40mph and 50mph speed limit)

HA 28/11/17 - The A5 Trunk Road (Witherley to M69 Junction 1)

(40mph and 50mph speed limit)

The proposals:

The perfectly good rural dual carriageway between the M42 and Dordon currently has a temporary 50mph limit — until a few years ago it was NSLA. This limit will be made permanent.

The 50mph section between Dordon and Grendon is to be reduced to 40mph. This is already a favourite spot for the Warwickshire CRP camera van.

The Atherstone bypass is to be reduced from NSLA to 50mph.

A reduction to 50mph or 40mph is planned along the 8-mile stretch between Witherley Island, Atherstone and the M69.

Reasons for objecting to the proposed reduction of speed limits

The claim that the speed limit reductions ‘will benefit communities on both sides of the A5’ is disingenuous for the following reasons:

Residents were aware from the outset of the prevailing A5 speed limits

They were aware that their homes were situated on the A5 Trunk Road

No-one forced them to buy homes on the A5 Trunk Road

The Atherstone bypass is to be reduced from NSLA to 50mph – this is absurd given the fact that there are NO frontages whatsoever.

Much of the 8 mile stretch between Witherley Island, Atherstone, and the M69 is entirely rural, yet a reduction from 50mph to 40mph is planned

Safety Reasons – Personal Injury Collision reduction

No evidence is provided to show that any of the Personal Injury Collisions were caused by vehicles travelling at, or in excess of, the current speed limit.

These limits have already been reduced previously. Clearly, this strategy has been unsuccessful in reducing Personal Injury Collisions and has therefore prompted more of the same failed medicine.

I believe the new limits will not just be unsuccessful in reducing casualties and fatalities, but will actually be bad for road safety.

I don’t dispute for a minute that there are times when drivers need to slow down. It's vital that they drive at a safe speed for the conditions and one that does not intimidate other road users, but speed lowered limits are too inflexible and too inexact to meet this aim.

Whilst accident reduction on any road is highly desirable, these limits are not the most effective way to achieve their aim and may, in fact, increase accidents. An artificially low for the road means that people will bunch, driving too close to the car in front. This in turn will lead to an increase in tailgating, overtaking and inattention accidents.

“Inattention” is the most common cause of collisions according to Police STATS 19 Forms.

Drivers forced to drive too slowly are more likely to risk dangerous overtakes through frustration and anger. This has already happened in other counties – Somerset and Suffolk to name just two.

Drivers will soon realise that the proposed limit is too low, and lose respect for other speed limits.

The new limits are set contrary to the advice in Government Circular Roads 1/80 and 1/93. These explain that speed limits are an ineffectual tool for lowering speeds. The Circular states:

Paragraph 5 — "Specific speed limits cannot, on their own, be expected to reduce vehicle speed if they are set at a level substantially below that at which drivers would choose to drive in the absence of a limit."

Paragraph 6.4 — "Speed limits should be lowered only when a consequent reduction in vehicle speed can reasonably be expected. A survey of traffic speeds should indicate whether a lower limit will, in the absence of regular enforcement, be likely to result in lower actual speed."

Although Warwickshire has previously chosen to set aside this advice, it is difficult to dispute that a road has a “natural” speed. When drivers are forced to drive below this speed, they become impatient, bored and are far more likely to attempt dangerous manoeuvres.

Excessively low limits in many places and are becoming a significant source of frustration to drivers. Warwickshire already has a plethora of new limits, and on many roads the limit can vary extensively within a few kilometres This leads to confusion, as many drivers become unsure of the current limit on a given stretch when they change so frequently.

Driving is too complex an activity to be reduced to a simple mechanistic process. The county’s speed limits already change frequently with limits rising and falling within a few meters of each other. This is encouraging a dangerous “driving by numbers” mentality and an over-reliance on speedometers as an indicator of safety.

The relationship between speed and accidents:

The ‘85th Percentile’ is the proven scientific method for setting speed limits. This refers to the speed of the 85th car out of 100, in ideal, free flowing traffic conditions, as being the safest speed limit for a given road. This speed is not influenced by faster vehicles travelling at an inappropriate speed, as is often (wrongly) claimed.

Attempts have been made to discredit the 85th Percentile as a tool for setting the maximum safe speed for a given road:

TRL 511 – The Need for Speed (Reduction)

High-level summary:

What is TRL 511?

TRL 511 is the report from the Transport Research Laboratory used by the DfT and Councils like Oxfordshire to justify reducing speed limits on the open road from 60mph to 50mph, and then enforcing them with cameras.

What does it say?

The report's conclusion is that reducing average traffic speeds will slash accidents, no matter what caused them. It supports this by comparing accident rates and mean speeds on different rural roads across the country.

What does it REALLY say?

Reading TRL511 in detail reveals that the initial assessment of 174 rural roads showed that accidents FELL with higher speeds rather than rose, because there were fewer hazards on the roads where people drove faster.

How did the authors turn the results around like this?

The report writers managed to turn this predictable conclusion on its head by splitting up the roads by hazard density into four different groups, and claiming that, within each of these groups, accidents ROSE with speed.

Is this approach valid?

The methodology used to reach this conclusion is flawed because it is invalid to compare accident rates between roads that carry different amounts of traffic, even if the roads are otherwise similar.

What use is TRL511?

TRL511 is a contrived report that really shows that more accidents happen where there are more hazards, and this is nothing to do with the average speed of traffic.

How has this distorted road safety policy?

The way to address road safety is to deal with the actual cause of real accidents. The authorities are using reports like TRL 511 to avoid telling the public what really causes crashes, using this statistical chicanery to falsely blame the responsible behaviour of the majority of motorists.

What effect has this had on road safety and wider society?

Various authorities then hide behind baseless and vacuous statements like "a 1mph reduction in average speed causes a 5% fall in accidents" to dismiss reasonable complaints about nonsensical speed limits and enforcement that is unrelated to safety. This has led to falling driving standards and mass breakdown in respect for law and order.

Background

When they legalised speed cameras in 1992, the authorities clearly intended from day one to use them to drive down general speeds by blanketing roads with them and reducing speed limits. Some of the worst examples of cameras being placed on straight rural roads and urban dual carriageways date from the very earliest days of the grey boxes. Some of these have even been taken down by camera partnerships, as they do not meet new visibility guidelines. Wholesale limit reductions began at the same time – the first batch of Oxfordshire rural 50mph limits dated from the opening of the M40 in the early 90's.

But they had a problem – all the road safety research that had been done supported the setting of speed limits at sensible levels, so there was no intellectual backing for their blanket speed reduction policy.

Quickly, they cobbled together a report known as "Finch et al." full of impressive looking statistical analysis of historical, international examples of speed limit changes. This created the absurd claim that a 1mph reduction in average speed would always cut accidents by 5%.

At a stroke, any concept of there being a "correct" and "sensible" absolute level at which to set a speed limit was swept away. However low a speed limit was, "Finch et al" would always justify lowering it further.

Finch et al is almost embarrassingly contrived, violating the most basic principles of statistical reporting.

Finch et. Al. is still quoted regularly as the authoritative piece of research that it is manifestly not. But the speed reduction brigade clearly felt they were skating on thin ice, so they commissioned two further studies to back up their position.

TRL 421 and TRL511 are the illegitimate love twins of "Finch et al", dealing with urban and rural roads respectively.

TRL 511 – What it Says

Lets look at TRL 511, which is being used to justify more rural 50mph limits on perfectly good roads.

The authors chose 174 rural roads or between 1km and 10km in length, all subject to the National Speed Limit of 60mph, and a mix of A, B, C and unclassified.

Then they measured the speed in ONE location on each of these roads for TWO WHOLE DAYS.

Armed with this less than sophisticated data and a sheaf of STATS 19 forms, they counted the number of accidents over a four-year period (about two per year per location), divided them by the measured traffic levels to get an accident rate.

Then they made an adjustment to this accident rate because it is well known that if you double traffic on a road, you never get twice as many accidents. Crucially, the formula they used to make this adjustment was a simplistic, linear one. This is the vital error in their argument.

They were then left with an adjusted accident rate from which all the known effects of different levels of traffic had been stripped away.

Then they plotted this accident rate on a graph against the average speed on each road.

One can only imagine their horror when they discovered that this accident rate FELL as speeds rose. Yes – the faster the road, the fewer accidents there were!

Any reasonable person would conclude that accidents are more likely where there are more hazards, but that the vast majority of drivers respond to those hazards correctly and this is why speeds are also lower in these places.

If there is a road with a straight bit and a dangerous bend, speeds will be slower around the bend but that is nonetheless where the accidents will occur, because one or two drivers out of thousands will attempt to take it too fast.

This is blindingly obvious, but for those who commissioned the TRL report, it does of course give:

THE WRONG ANSWER!

Undeterred, the authors split the sample roads into four different types of roads, based on the density and nature of hazards such as bends, hills and minor junctions. They then assumed that all of these roads were identical both with each other and along their entire lengths. They called them "homogeneous" roads.

Lo and behold, when they looked at each of these four types of "homogeneous" road separately, they found that within each of these types they got the answer they wanted – a nice little graph showing how accident rates increase with average speed.

They finished the report by showing how many lives could be saved by reducing rural speeds in accordance with their cosy little mathematical equation.

A CRITICAL ASSESSMENT

This report contains no assessment whatsoever as to the causes of any of these accidents, and whether excessive speed was put down as a causal factor on the STATS 19 forms, which were available to the writers of TRL511.

I can think of no rational reason why the authors of any report on road safety would ignore this vital information and approach the study in the way it was actually done. Other than, of course, the need to arrive at a pre determined answer to support existing policy.

All of the roads, even when they are split into these homogeneous groups, will vary along their length, with some straight bits and some bits with bends and junctions. Speeds on the straight bits will be higher, but accidents on the slower, bendy bits will be more numerous. That doesn't change. And the average speed of thousands of
drivers in on single location still has nothing to do with the actual speed of the one or two drivers who crash somewhere else on the road.

But that's realty – these people don't recognise such things, and they would just point to their equations and say they demonstrated that the link was there, and that it was statistically significant!

There is, however, a systematic flaw in their reasoning which points to an erroneous explanation for their results. Put simply, they have shot themselves in the foot.

THE FLAW

They have allegedly created four groups of roads that are so comparable, so "homogeneous", that both speeds and accident rates can be directly compared between roads in the same group. This in itself is contrived and unlikely – these sorts of roads vary by the hour and by the 100 yards – but we accept that these variations would be random and wouldn't explain the result they obtained in the report, so let's bear with them for a moment.

If these roads were that similar to one another, then why on earth would the average speed of traffic be different? Why do they have a variable to measure at all? If the hazard spread and road width is the same, why should Lincolnshire drivers choose a different speed from Gloucestershire ones?

By claiming that the roads are identical, the authors of the report have left only one reason for the average speed to vary – traffic levels. As a road gets busier, the average speed will drop, even in free flowing conditions, as the faster drivers are more likely to be held up by slower ones and overtaking opportunities diminish.

Now the authors of the report had gone to great lengths to strip out flow difference effects from their calculations – they made a great play of trying to isolate the mean speed variable by stripping away "masking factors" like traffic levels and road geometry, leaving mean speed as the only variable.

The way they did this was to assume that a doubling of traffic levels would increase accidents not by 100% but by 65%, and adjust the accident figures accordingly.

HERE'S THE PUNCH LINE

They have already made an adjustment to the accident rate to strip out the effects of different levels of traffic. That INCLUDES any effects that might accrue from changes in speed caused by changes in traffic volumes!

There aren't any variables left. All they have done is to prove that 0=0! Their methodology strips out the very thing they are trying to measure, and they should end up showing a flat graph, with no variation between speeds and accidents.

The fact that they don't can mean only one of two things:

1 There is some other factor causing the difference in speeds between different but " homogeneous" roads, in which case they are not homogeneous and it is invalid to split them into the four groups without finding out more about the causes of speed variation. One can only speculate what these causes might be – different driver demographics, vehicle types (tractors!), traffic density profiles through the day and so on. Any one of these could also affect accident frequency on a systematic "common cause" basis.

2 Their 65% equation for adjusting accident rates for traffic flows is over simplistic and contains a systematic error which is small enough to be masked by the reductions in hazards in the overall numbers but is revealed when the variations in hazards are reduced in the four homogeneous groups.

Evidence to support the assertion that the analysis in TRL511 is fatally flawed comes from the TRL itself. TRL's Published Project Report PPR026 (Accident Analysis on Rural Roads - a technical guide), contains the following statement in paragraph 4.15:

"The relationship between accidents and vehicle flows is not a linear one (e.g. see Walmsley and Summersgill, 1998). For this reason, it is recommended that roads with very different flow levels are not studied together."

Conclusions

Rather than reducing deaths on the road, these limits are likely to lead to more accidents. They are too low for many of the roads and will lead to drivers and riders losing respect for more sensibly set limits. The County already has an excess of limit changes and artificially low limits, and drivers are becoming confused.

Instead of a lower limit, I believe a series of vehicle activated signs (VAS) should be use to indicate specific hazards. These have been shown to have a marked effect on accident rates, do not interfere with free-flowing traffic, and do not cause frustration amongst drivers and riders. TRL548 clearly shows that not only will VAS reduce vehicle speeds, but also being warned of approaching hazards leads to lower accident rates.

I urge the installation of vehicle-activated signs, rather than impose yet more lowered limits.

Regards,

Paul Biggs