Dianthus Medical Blog Archive

The medical ethics of an 80 mph speed limit

Can you put a price on a human life?

The instinctive answer of many people to that question is "no", but most health economists would say that not only can you put a price on a human life, you absolutely need to do so. Certainly when running a health service, the only rational way to decide whether interventions make economic sense is to do exactly that.

Health Technology Assessments from NICE use the principle of valuing a human life when they make decisions about whether health interventions are cost effective on the NHS. They set a threshold of £30,000 as the price of one year of life in good health, although it's not necessarily rigidly applied in all cases. What an appropriate threshold should be is of course a matter of great debate, but the fact that a threshold exists above which it is simply not rational for society to pay to save a life is not controversial. As I have argued before, more than once, it is essential to put a value on human life in this way when resources are finite, as of course they always are.

Now, the government has recently proposed increasing the speed limit on motorways from 70 mph to 80 mph. I think it's quite interesting to consider the question of putting a value on human life in this context. The government argues that there would be economic benefits to increasing the speed limit, in that people would get to their destination faster, thus saving time, and we all know that time is money. On the other hand, we would also expect that raising the speed limit would lead to more crashes and more deaths.

As an aside, I do not see the argument of economic benefits as completely self-evident. It is certainly not true that car journeys will automatically take 7/8 of the time they took previously. A typical motorway journey includes time spent driving between urban start and end points and the motorway, stopping at a services for a coffee break on longer journeys, and time spent driving slowly in congested sections of motorways. None of those would be affected by the speed limit. So time savings would, in percentage terms, be small. There is also a possibility that, counter-intuitively, faster speed limits could even slow down journey times, as they may increase the risk of congestion. One widely used scheme for reducing congestion, most famously used on the M25, is to decrease speed limits when traffic is heavy, thus reducing stop-start driving that leads to congestion.

And, of course, any economic benefits of faster journey times would be offset by increased fuel consumption. Wind resistance increases with the square of speed, so there is more difference than you would think between 70 mph and 80 mph in fuel consumption.

So, while there may be economic benefits to increasing the speed limit, I would like to see how they have been calculated before I believe that they exist.

But anyway, let us accept for the sake of argument that there are economic benefits to increasing the speed limit, as that is how we get into the interesting ethical question.

Suppose that the economic benefits to the UK economy as a whole, taking account of the net effect of faster journeys and increased fuel consumption, were to be reliably estimated at, say £10 million (that's a figure plucked entirely out of thin air just for the sake of argument, and I make no claim whatsoever that it's even remotely close to the true benefit).

Let us then suppose that the number of excess deaths and injuries could be reliably estimated (which of course is also difficult), and then converted to an economic value using NICE's threshold of £30,000 per quality adjusted life year.

The interesting ethical question is then this: if the figure we arrived at for the economic costs of the excess deaths and injuries was less than £10 million, would we be justified in concluding that increasing the speed limit was worthwhile?

A simplistic analysis would suggest that the answer is yes, but I don't think it's as simple as that.

The problem is that many people believe that there is a real moral and ethical difference between actively killing someone and passively failing to save a life. When NICE makes decisions based on the cost of a human life, it does so based on how much it costs to actively intervene to save someone who would have died without intervention. People killed in road traffic crashes on motorways will have been killed by human agency.

Is it therefore appropriate to use the same cost effectiveness threshold? I think the answer to that is probably no.

However, it gets more complex still. Imagine this thought experiment. Suppose that you could identify an individual person whose existence was known, with certainty, to be thoroughly detrimental to the UK economy. Let's call him George (no, of course I'm not thinking of Mr Osborne, this is a purely hypothetical thought experiment). After doing careful calculations, we know for a fact that killing George would boost the UK economy by £10 million. Who thinks we should kill him? I would guess not many. While we are generally prepared to accept that there are economic limits on saving lives, I doubt that many people would want to kill a specific, named individual, no matter what the economic benefits of doing so.

The speed limit situation is somewhere in between the two extremes. We will be actively killing people, but we don't yet know who those individuals are. We won't even know with certainty even after we have killed them: increasing speed limits only increases the risk of death, it does not create it where it did not exist before. Anyone killed on a motorway after the speed limit increase might have been killed even had speed limits stayed the same.

So are the excess deaths due to an increased speed limit morally and ethically equivalent to not funding an expensive medical intervention, deliberately killing George, or somewhere in between?

My own feeling is that there probably is a threshold of cost on a human life which could be set here, but that it would be much higher than the £30,000 used by NICE. What do you think? Let me know via the comments form below.

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