Nov 05

Seat belts: another look at the data

I am grateful for a question posted today by Carsten Jasner in response to an earlier post of mine – Seat belts again. It has prompted another look at the data:

Very interesting! But when the number of car occupant deaths increases while the number of all road user deaths decreases how can the number of pedestrians and cyclists [deaths] also increase?

Figure 1, all road accident deaths (excluding motor cyclists), shows that a well-established downward trend was interrupted (by the seat belt law?) and replaced by a slightly rising plateau. After the seat belt law (arrow) total deaths did not fall below the 1983 level until 1991.

Figure 1

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(Source of statistics: http://www2.dft.gov.uk/adobepdf/162469/221412/221549/227755/rrcgb2009.pdf)


For many decades, as car ownership increased in Britain the number of people moving about in cars also increased while the numbers moving about on feet or bicycles, and exposed to the risk of road accidents, fell sharply. Part of the decline in walking and cycling can be explained by the shift to car travel; another part by the fact, that as the volume of metal in motion increased, children were withdrawn from the threat, while vulnerable adults, especially cyclists, withdrew themselves. Figure 2 shows a dramatic decline since 1930 in the ratio of pedestrians and cyclists killed to car occupants killed – from 5.95 in 1935 to 0.47 in 2006.

Figure 2

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Figure 3 zooms in on more recent years. Between 1970 and 1982 the ratio dropped from 0.96 to 0.81. In 1983, the first year of the seat belt law, the ratio jumped sharply to 1.00, before resuming its historic downward trend, but it did not drop below 0.81 until 1989. This sharp jump is of course exactly what one would expect in the light of the decrease in car occupant deaths and increase in pedestrian and cycling deaths coinciding with the seat belt law noted earlier. The step change in the trend suggests that each year since 1983 the seat belt law continues to deserve credit for the deaths of vulnerable road users, who but for the law would still be with us.

Figure 3

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Oct 28

Moral hazard: bonuses, seat belts and condoms

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“Moral hazard is a term that dates back to the 1600s. Until recent times its use has been mostly confined to the insurance industry to refer to behaviour that responds to changes in perceived risk.

The industry has noticed that people who have contents insurance are less careful about locking up. It has also noticed that drivers of cars with ABS brakes (superior brakes) did not have fewer accidents they had different accidents accidents consistent with high-performance cars, which is what they had become.

Why moral hazard? Clearly the insurance industry was disconcerted by behaviour that upset the calculations of its actuaries. Such behaviour had to be wrong immoral. But such behaviour is universal. Risk management is an exercise that involves striking a balance between the potential rewards and losses of decisions made in the face of uncertainty. A less judgmental term to describe this phenomenon is risk compensation. Legislators and regulators routinely ignore it.

Britain is suffering simultaneously from under-regulation and over-regulation. The deregulation of the financial markets under Margaret Thatcher gave a relatively small number of bankers free rein to contrive incentive structures that paid them fabulous rewards for taking risks with other peoples money. Meanwhile other spheres of activity are being suffocated by an excess of regulation, the most egregious example being the Independent Safeguarding Authority. This new bureaucracy, created as a response to the murder of two young girls in Soham, is charged with vetting an estimated 11.3 million people before they will be permitted to work, or volunteer with, children or vulnerable adults. The vetting involves a Criminal Records Bureau check on all 11.3 million after which we will decide on a case-by-case basis whether each person is suited to this work.

Leaving aside the mind-boggling expense and bureaucracy required to perform this feat, its effect is almost certain to be perverse. A CRB check will be seen as an insurance policy; behaviour that might previously have aroused suspicion is now less likely to be questioned because some superior authority has certified the suspect as safe.

After the Thatcherite deregulation, under New Labour we have had the Better Regulation Commission, the Better Regulation Executive, the Better Regulation Advisory Council and now BERR the Department for Business, Enterprise and Regulatory Reform. All these attempts at reform have explicitly acknowledged the damage caused by excessive regulation and have been powerless to resist it. Fundamental to this failure is a blindness to risk compensation.

Every perceptible safety measure that does not make the people want to be safer will provoke offsetting behaviour. The effect can be seen wherever one looks from protective equipment on the sports field, to the settlement of flood plains protected by higher levees, to bailed out banks. It can be found on the road and in the bed condoms are seat belts for sex concludes one study that invokes risk compensation to explain the failure of both safety measures to deliver the protection they promised.

Which takes me to my final point. The College of Emergency Medicine is leading a campaign to make cycle helmets compulsory. If successful it will result in a significant decline in cycling with a loss of attendant social, environmental and health benefits with no life saving benefit. It will kill off Londons new cycle hire scheme. In support of their campaign they cite the success of the seat belt law. But the law has failed and should be repealed. The Parliamentary Advisory Council of Transport Safety resolutely refuses to acknowledge evidence of this failure (click here, here and here). In its blindness to risk compensation and its consequences it risks helping to create a new, genuine, moral hazard.

PS    The Manifesto Club campaigns against the hyperregulation of everyday life. It has a refreshing website – http://www.manifestoclub.com/.

Oct 21

Safety Fears Stop Bikes For Africa

This is one I have to share

Found on an excellent website – http://www.copenhagenize.com/

18 September 2009

“Here’s an appropriate little ‘wedgie’ in the Fear of Cycling series. The Isle of Wight County Press Online [big name for a little paper :-)] reports that the Hampshire Constabulary has cut off supplying unclaimed stolen bikes to a charity that sends bikes to Africa.

They are, get this… afraid of being sued if someone gets hurt whilst using one of them. You’d think that they were talking about barrels of toxic waste.”

Here’s the link to the article.

Oct 16

Final open letter to Executive Director of PACTS

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To Robert Gifford

Executive Director, The Parliamentary Advisory Council for Transport Safety

Dear Rob

Failing a response, I propose to draw this one-sided correspondence to a close. I believe that I have established:

a. that the claim that seat belts have saved 60000 lives since the implementation of the seat belt law is nonsense, and

b. that it is your (PACTS) view that a measure that could be demonstrated to save the lives of motorists would be OK so long as the number of vulnerable road users killed as a result is smaller. I pressed you on this point in open letters 2 and 3 and you have not, as yet, denied it.

When you sent me the paper by Richards et al that I discussed in my third open letter you said the paper highlights the difference between the number of lives saved overall through the use of seatbelts and the number saved through the implementation of legislation in 1983. I take it from this that you accept these highlights as validation of the claim still on your website that seat belts have saved 60000 lives since 1983.

In my third open letter I said that with such a sudden large increase in the wearing of seat belts (140%) one should see a sudden large downward step in the established downward trend. I asked Where is it? I have found it! I was looking in the wrong place.

In the graph below I have reconstructed the analysis of Richards et al that highlights the difference between the number of lives saved overall through the use of seatbelts and the number saved through the implementation of legislation in 1983.

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To accept the claim in the paper by Richards et al that seat belts saved 2500 lives in 1983 you have to believe that 1869 extra lives were saved by seat belts compared to the year before. Since you cannot see such a dramatic effect in the graph of actual fatalities you are forced to believe that in 1983, coinciding with the implementation of the law, there was some dramatic increase in danger on the roads that, but for the seat belt law, would have killed 1869 more car occupants. Even people who can believe six impossible things before breakfast would find that a bit of a stretch.

Why am I doing this? Why am I trying to resolve this issue via open letters on my website? I have no personal desire to cause embarrassment, but earlier attempts to sort this out via personal emails have run into the sand.

In a parliamentary debate in 1979 William Rodgers, then Secretary of State for Transport, claimed On the best available evidence of accidents in this country evidence which has not been seriously contested compulsion could save up to 1000 lives a year” (Hansard, March 22, 1979). This clearly did not happen, but the myth has grown and PACTS has been complicit in this growth.

Consider the following more recent parliamentary exchange in a debate about compulsory cycle helmets:

Mr. Kevan Jones (North Durham) (Lab): There are some who would accuse my hon. Friend of extending the nanny state. Does he agree that the same arguments were used in the 1960s and 70s against the wearing of seat belts, and that the legislation passed in that respect has reduced the number of deaths and the personal tragedy experienced by families whose members would otherwise have died on the roads?

Mr. Martlew: My hon. Friend is perfectly right. We have always seen a knee-jerk reaction against such measures, whether on the wearing of seat belts or preventing drink-driving, but, after a while, such things become common sense and we wonder why we did not do them before. (Hansard 23 Apr 2004 : Column 529)

Your website proclaims that PACTS was set up as part of the fight to get mandatory seatbelt wearing turned into legislation. The success of the seat belt law might fairly be described as PACTS foundation myth. It is not a bit of harmless exaggeration.

You have accepted that the law caused an appreciable number of extra deaths among pedestrians and cyclists. Further, as we have seen above, the myth is now being invoked to promote another myth about the efficacy of cycle helmet legislation. So profoundly embedded in the parliamentary mind is the success of their seat belt law that no one saw reason to question the assertion of Mr Jones. A compulsory helmet law would significantly impair efforts to promote cycling and kill the London cycle hire scheme; no potential user of the scheme would want to put on a sweaty helmet that did not fit, and no scheme has been proposed to provide clean well-fitting helmets for spontaneous users. For a comprehensive over-view of the cycle helmet law debate please visit nohelmetlaw.org.uk.

Oct 06

Third Open Letter to Executive Director of PACTS

To Robert Gifford

Executive Director, The Parliamentary Advisory Council for Transport Safety

Dear Rob

Thank you for sending me a paper claiming that seat belts have saved 57000 lives in the UK between 1983 and 2007.  Is this the source of the 60000 claim posted on  your website in 2008?

I have discovered that the paper you have sent me (by DC Richards, R Hutchins, RE Cookson, P Massie and RW Cuerden) is accessible on line at http://bast.opus.hbz-nrw.de/volltexte/2012/527/pdf/ .  

The paper documents an increase in seat belt wearing rates for drivers of well over 100%. I have no reason to doubt the accuracy of the data represented in their Figure 6.

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Figure 6. Effect of seat belt legislation on seat belt wearing rates for car drivers


It then estimates that seat belts are 61% effective in preventing fatalities in crashes. The fact that wearing a seat belt considerably improves ones chance of surviving a crash is also not disputed.

It then calculates (their Figure 5) how many lives have been saved by seat belts since the UK law came into effect.

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Figure 5. Number of car occupant casualties prevented by seat belts


It also presents a graph showing how many fatalities remain. (their Figure 4)

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Figure 4. Fatal and serious car occupant casualties


And herein lies a mystery.

Richards et al have charted a large increase in the use of a safety measure that provides significant protection in crashes. This measure they claim saved over 2500 lives a year (and rising!) in the first 8 years of the law. With such a sudden large increase in the adoption of such an effective safety measure one should see a large downward step in the established downward trend. Where is it? One cannot see any effect in the graphs here and here . Richards et al dont even look for it; their graphs dont start until 1983. They appear remarkably uncurious about why it should be that in the first eight years after the law the more lives seat belts were saving (Figure 5), the more car occupants were being killed (Figure 4). And they display no interest in the possibility of risk compensation: factors such as any change in driving behaviour for occupants who do / do not wear a seat belt were not taken into account (p 229).

Further they make no comment on the fact that the reduction in driver fatalities that did occur in 1983 (the year in which evidential breath testing was introduced) consisted almost entirely of drivers with alcohol in their blood.

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Great Britain driver deaths by place and alcohol level in dead driver. Source: Broughton and Stark 1986


Three questions:

1.Do you consider that the paper by Richards et al validates the 60000 claim still on your website?

2.If so can you explain the absence of the large downward step that should appear in the graphs here and here ?

3.Can you explain why seat belts were so extraordinarily selective in saving the lives of drivers who had been drinking?

Finally you say:

I do not wish to be drawn into the debate about the benefits/disbenefits of cycle helmets. PACTS aim must be to improve the safety of all classes of road user and tackle the issue of the disproportionate risk placed upon those least able to protect themselves.

It was not my intention to draw you into a debate about the benefits/disbenefits of cycle helmets; the PACTS reporton this subject seems to me to be admirably clear and balanced. But I am interested in PACTS aspiration to tackle the issue of the disproportionate risk placed upon those least able to protect themselves.

I am seeking confirmation of a point I raised in my last open letter. From your Significance article it appears that it Is PACTS position that a measure that saves the lives of motorists is justified so long as the number of vulnerable road userskilled as a result is smaller. Is this your position?

Sep 30

Second open letter to Executive Director of PACTS

To Robert Gifford

Executive Director, The Parliamentary Advisory Council for Transport Safety

Dear Rob

Im sorry but I must persist. The power and endurance of the myth that PACTS and RoSPA have built around the seat belt law takes a lot of deconstructing. So long as belief in the efficacy of the law persists it will continue to serve as one of the principal arguments of the campaigners for compulsory cycle helmets.

Seat belts and helmets are routinely linked. Injury lawyers argue helmetless injured cyclists risk having their compensation reduced for contributory negligence in the same way that unbelted motorists would. (see also here) Earlier this year the Mississippi Senate threw out a bill to repeal the States mandatory cycle helmet law on the grounds that the helmet requirement was similar to the states seat belt law, designed to protect people from avoidable injuries.

You say in response to my earlier letter While I entirely accept that the piece on our website referring to the estimate of 50,000 lives [60000 actually] could have been more appropriately worded, I cannot share the view that seat belts have not been an effective contribution to casualty reduction.

Short of a complete public retraction I cannot imagine an appropriate way to refer to the 60000 claim. The claim that the seat belt law has saved 60000 lives is ludicrous. I accept that the number was not your invention, but so long as it remains on your website, it strongly implies to the reader that PACTS considers the claim to be valid.

I ask you to re-read this passage on your website:

On the 31st January 2008, the 25th anniversary of the law change which made front seatbelt wearing compulsory was celebrated. PACTS itself was set up by Barry Sheerman MP as part of the fight to get mandatory seatbelt wearing turned into legislation. Eight years later it became compulsory for all backseat passengers to use seatbelts and it is estimated that since the introduction of the first law change in 1983, seatbelts have prevented 60,000 deaths and over 670,000 serious injuries.

As most parliamentarians, and the rest of the world, will read it, PACTS is celebrating its role in saving 60000 lives. Indeed this piece of self congratulation identifies the seat belt law as the foundation stone of your organization.

In your article five months later in Significance (June 2008, sadly available free only to those with institutional access to electronic journals) you concluded that in the first year of the law it had saved not 2400 lives but 164 net. Here (for those without access to electronic journals) is Table 1 from your article.

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In your article from which this table is taken you say: The best estimates are that extra deaths to vulnerable road users did accompany the introduction of mandatory wearing of seat belts.

In your response to my article advocating repeal of the seat belt law you do not comment on my point that most of the decrease in car driver deaths in 1983 consisted of drivers who were over the alcohol limit (down 14%), and that this coincided with the introduction of evidential breath testing. Do you think that this change in the law with respect to drinking and driving had no effect?

In your Significance article you are clear that you believe the law has saved the lives of people in cars at the expense of vulnerable road users: The picture shows a clear reduction in death and injury to car occupants, appreciably offset by extra deaths among pedestrians and cyclists.

You then proceed to defend the law as follows: It would be a severe constraint on the use of safety measures if any measure were to be ruled out for which the larger number of deaths and injuries saved were differently distributed among road user groups from the smaller number resulting from the measure The wearing of seat belts is therefore not exceptional among safety measures in that extra deaths and injuries that may arise from wearing occur in part (only in part because, if wearers drive more riskily, some of the extra deaths and injuries will occur to vehicle occupants) to different road user groups than those among which deaths and injuries are preventedthough the difference is perhaps sharper for belt wearing than for many other measures.

I take this passage to mean that you think a measure that saves the lives of motorists is OK so long as the number of vulnerable road users killed as a result is smaller.

In the light of that argument I would welcome your comment on this analogy: an Organ Harvester Lottery in which healthy people will be selected at random to donate organs to people in need of them. One heart and one liver could save two lives at the cost of one slightly better than the ratio that you argue justifies keeping the seat belt law. Throw in two kidneys and you get a four to one ratio of lives saved to lives lost. This is a gruesome but not wholly inappropriate analogy given the myth circulating at the time – (and still) that the success of the seat law was responsible for increasing the shortage of donor organs.

I do hope that you will take the trouble to comment on my website. Now that the campaigners for compulsory cycle helmets are on the march again that part of their evidence invoking the success of the seat belt law needs renewed scrutiny.

Best wishes

John

Sep 23

Open letter to Executive Director of PACTS

To Robert Gifford

Executive Director, The Parliamentary Advisory Council for Transport Safety

Dear Rob

This claim made over a year ago is still on the PACTS website:

On the 31st January 2008, the 25th anniversary of the law change which made front seatbelt wearing compulsory was celebrated. PACTS itself was set up by Barry Sheerman MP as part of the fight to get mandatory seatbelt wearing turned into legislation. Eight years later it became compulsory for all backseat passengers to use seatbelts and it is estimated that since the introduction of the first law change in 1983, seatbelts have prevented 60,000 deaths and over 670,000 serious injuries.

I have demonstrated the claim to be nonsense: click here and here. A while ago I invited you to post a comment on this demonstration of nonsense on my website. You have declined to do so, so I now issue a more public invitation.

Borrowing from Churchill – the lie has got all way round the world before truth has got its pants on. If you Google the claim you get thousands of hits. Legislators like to believe their laws make a difference. If the BBC, the DfT, PACTS, RoSPA and Google all tell them their seat belt law has saved 60000 lives they will be inclined to believe it.

Why does it matter? The Association of Paediatric Emergency Medicine and the College of Emergency Medicine are now lobbying vigorously for a law that would make cycle helmets compulsory for children, and ultimately for all cyclists . Campaigners for cycle helmet laws routinely cite the success of the seat belt law. Their argument is seductively simple: seat belts and helmets reduce injuries in crashes; seat belt laws have saved lives and so would a helmet law.

The PACTS website is one of the ways in which your advisory council conveys advice to parliament. On this issue it has misled parliament. If parliamentarians are misled about the success of their seat belt law they are in danger of making the same mistake with a helmet law. I suggest that if you cannot refute my demonstration that the claim that the seat belt law saved 60000 lives is false, you should not just quietly remove it from your website, but retract it in a highly public manner.

The PACTS 2004 Parliamentary Briefing on cycle helmet use and effectiveness presents the case against compulsion in a clear, balanced and convincing way. It would be a great pity if it were to be undermined by pro-compulsion campaigners citing other PACTS evidence for the efficacy of the seat belt law.

I know it is difficult to admit to a clanger. But if you had devoted a moments thought to it you would have noticed that the DfTs claim that the seat belt law had saved 60000 lives was preposterous. If you and RoSPA persist in endorsing the DfTs claim you will assist in the promotion of a further nonsense that will inhibit efforts to increase cycling.

Best wishes

John

Sep 22

Seat belts – from the archive

Now in retirement and culling my files in the process of downsizing I came upon the following letter from the Royal Society for the Prevention of Accidents dated 7 July 1981 shortly before Parliament was to vote on a seat belt law, and encouraging Parliament to vote for the law:

TO ALL MEMBERS OF PARLIAMENT

Dr. Adams has recently published a paper advancing the thesis that the wearing of seatbelts may actually increase road accidents by encouraging a sense of false security. His paper presents road accident trends in several foreign countries to support his view. His paper requires detailed analysis. For the time being his thesis remains unproven.

25 years on RoSPA claims that the law has saved 60000 lives. Has it?

Sep 16

Seat belts again

Yesterday when I showed Mayer Hillman the graphs in my last blog on this subject he complained that they displayed the statistics for all road user deaths and not the statistics for those affected by the seatbelt law, i.e. people in the front seats of cars.

My excuse was that at the time I produced the graphs, almost 20 years ago, I was focused on total numbers because of the evidence that the law coincided, in Britain and elsewhere, with increases in the numbers of pedestrians and cyclists killed. Also, at that time no one was claiming that the law had saved anything remotely approaching the recent claim by the Government, RoSPA and PACTS of 2400 lives saved per year.

But stung by Mayers insistence that the claimed saving of 2400 lives per year was more than the total number of car occupants killed, I went back to the numbers.

The graph below shows the data for the same period for car occupants only. I asked the computer to fit a line to the data up to and including 1982 (the year before the law came into effect, small red arrow) and it produced the downward sloping trend displayed. When asked to fit a line to the statistics after the seatbelt law the computer replied with an upward trend. When the claimed 2400 lives saved is displayed on the graph it shows that the law should have brought impressive numbers back from the dead. The claim would appear to be based on the work of creationist statisticians.

picture-8Source: Road Accidents Great Britain: 1982 & 1989, Table 5,  HMSO.

Sep 11

Drugs prohibition

Simon Jenkins wrote an exceptionally powerful piece in the Guardian on 4 September entitled The war on drugs is immoral idiocy. His title conveys the essence. He went beyond proposals to decriminalize consumption, to advocate decriminalizing production as well to be replaced by licensing, regulation and taxation. The Guardian appears to be suffering a failure of nerve on this sensitive subject. Although Jenkins article generated an enormous on-line response 602 comments the last time I looked it published no letters, including mine!! So being my own publisher I reproduce it below.

Simon Jenkins says The mountain that must be climbed is licensing, regulating and taxing supply. The Sherpas have made a start. In 2004 the Cabinet Office Strategy Unit published a report entitled Alcohol Harm Reduction Strategy for England. It had a foreword by Tony Blair. He said:

Millions of us enjoy drinking alcohol with few, if any, ill effects.

But: The Strategy Units analysis last year showed that alcohol-related harm is costing around £20bn a year, and that some of the harms associated with alcohol are getting worse.

So: The aim has been to target alcohol-related harm and its causes without interfering with the pleasure enjoyed by the millions of people who drink responsibly.”

Ultimately he argued, it is vital that individuals can make informed and responsible decisions about their own levels of alcohol consumption. Everyone needs to be able to balance their right to enjoy a drink with the potential risks to their own and others health and wellbeing.

He concluded: I strongly welcome this report and the Government has accepted all its conclusions. These will now be implemented as government policy and will, in time, bring benefits to us all in the form of a healthier and happier relationship with alcohol.

A cut and paste job on the alcohol harm report, replacing alcohol with drugs, would go a long way to producing a Drug Harm Reduction Strategy. It contains no mention of prohibition.