Tesla cars and risk homeostasis.

[Mike Sales]

There is an interesting article in The Slate about Tesla cars and road safety.
It makes several interesting points but this paragraph, not strictly about robot cars, struck me.

Researchers have cited this shift toward bulky SUVs and trucks as a key factor in the rising number of vulnerable road users killed on American roadways. Traffic deaths among people inside automobiles, meanwhile, have fallen 28 percent in the last 40 years. Notably, drivers who feel safer behind the wheel may drive more recklessly, assuming that they’ll come out of it OK if they end up in a crash (this is the Peltzman effect, named after an economist who argued that seat belt laws induced riskier driving). Pity the pedestrian or cyclist struck by a driver who felt secure in a Hummer that weighs as much as an elephant.

That same logic holds for cyclists and pedestrians, more of whom are being killed on American roads—by all kinds of automobiles—than at any time since George H.W. Bush was president. These “vulnerable road users” have no control over the design of American autos, which are growing heavier, taller, and more dangerous to people walking or biking. For years, the federal government has focused on automobile occupants, doing little to protect vulnerable road users beyond recommending that they “dress to be seen by drivers.”

https://slate.com/technology/2021/08/te ... lever.html

[Jdsk]

Interesting article. Thanks for posting.

It's strong on the need for better evaluation, and why that needs to cover the whole system. It's probably right on the adverse effects of heavier passenger vehicles. I'm not sure that Tesla could have done much more on their own.

It's weak on the statistics, see below.

It's now essential to consider effects of improvements on safety on behaviour. But the article has very little on "risk compensation" or "risk homeostasis". And any discussion on this should take into account what's known on the subject and include recent systematic reviews, for example:
https://www.bmj.com/content/370/bmj.m2913

Jonathan

USA data
https://www.iihs.org/topics/fatality-st ... edestrians

[Stevek76]

Denying risk compensation is like denying climate change, or the moon.

I dealt with the review on the h matter in that forum, most of the studies it reviews clearly didn't understand the concept and were effectively case control studies on existing usage with not very much effort at the control part and extraordinarily crude measurements of 'risky behaviour'.

It's just as applicable to cars also, a large car at 30 feels considerably slower than a small city car at that speed.

How much it's applicable to 'autopilot' Vs other driver assist systems is an interesting question, an issue here is Tesla's highly irresponsible marketing in giving a system comparable to its competitors assistance systems such a misleading name. At least once person has lost their head over the matter (literally). They have form in this matter though with the daftly distracting 'infotainment' system and gamifying the car with spaceballs references.

That said my suspicion is that as far as pedestrian and cyclist casualties go, the much bigger issue is just the sheer mass and high fronted nature of these vehicles that make them far more deadly when a crash happens.

I'm not sure what, if any, test the US has for this but the euro ncap pedestrian rating is immensely flawed. Essentially they just chuck a dummy head at a stationary vehicle at a certain 'height' in a wraparound sense which is not only a physics understanding fail but also means the bonnet below that point can be whatever it wants, hence the proliferation of massive grille vertical bonnets that stop a few cm below the test head impact point.

Smaller child or fancy your kidneys? Tough.

[Mike Sales]

I apologise if this has been posted before.
And because I have veered into mentioning helmets outside the ghetto.

Steve wrote.

Denying risk compensation is like denying climate change, or the moon.

There is an interesting discussion in the BMJ on risk compensation.

https://injuryprevention.bmj.com/content/7/2/89

We accept the principal finding of their review—that protective helmets protect in the event of an accident—but not the policy conclusions that they derive from it. The issue that divides us is risk compensation—does the behaviour of cyclists change as a consequence of wearing a helmet in ways that offset the protective benefit of helmets in accidents? After briefly referring to selected references from the safety literature on cycling, motorcycling, and driving, Rivara and the Thompsons assert that “the empirical evidence to support the risk compensation theory is limited if not absent”. Certainly such evidence is limited or absent from the sources they choose to cite—with a notable exception which we discuss below. We find abundant evidence for risk compensation.

It is important to distinguish between evidence for risk compensation in general—which is overwhelming, and evidence relating to cycle helmets—which is limited. Let us consider the general evidence first. Rivara and the Thompsons recommend readers to consult James Hedlund's article in Injury Prevention entitled “Risky business: safety regulations, risk compensation, and individual behaviour”.2 We strongly support their recommendation. They quote James Hedlund: “I believe the evidence is overwhelming that every (our italics) safety law or regulation is not counterbalanced by compensating behaviour”. But Hedlund also makes clear that the evidence is overwhelming that some laws and regulations, as well as safety measures voluntarily adopted, are counterbalanced by compensating behaviour. He states:

“We all change our behaviour in response to changes in our environment. Safety measures change our environment, so we may change our behaviour in response to them. . . . Never assume that behaviour will not change”.

Hedlund helpfully sets out four rules for judging the circumstances in which behaviour might or might not change:

If I don't know it's there I won't compensate for a safety measure. Bicycle helmets manifestly fail this test.

If it doesn't affect me, I won't compensate for a safety measure. He poses the question “Do I feel safer wearing a bicycle helmet?” and suggests that if the answer is yes compensation is likely to occur.

If I have no reason to change my behaviour, I won't compensate for a safety measure. Only if the behaviour of cyclists is completely unmotivated by concern for safety are they unlikely to compensate for a safety measure such as a helmet.

If my behaviour is tightly controlled I won't compensate for a safety measure. He singles out driving as an activity that offers very considerable freedom to compensate. Cycling offers at least as much.

Hedlund advises “to reduce or eliminate risk compensation, use measures rating low on at least one factor”. Cycling scores high on all four. Of all the cases Hedlund considers perhaps sports offer the closest comparators.

[Jdsk]

It's a mechanism that might occur. It shouldn't be assumed to be present. It should be looked for.

Jonathan

[simonineaston]

My chums & I were discussing something along these lines last week-end. Our lament was that the many developments in technology always seem to benefit the vehicle driver, and not other road users. Thus eg Volvo, a manufacturer with an excellent reputation for designing safety into their products, proudly report that they "put people first" however a closer examination of their designs reveals that they are firmly aimed at those inside and are not intended to protect pedestrians or cyclists very much at all!
Thinking about the wide range of technology that's appearing in modern cars, it's quite apparent that the designers could add all sorts of ideas that would protect anybody involved in an accident who was outside the vehicle, but they choose not to. We wondered why that was the case.
We noted too that there has been a recent new edition of the Highway Code in which pedestrians & cyclists have been moved up the scale of priorities. We worried that this development would simply act as a red rag to many drivers...
We went further by trying to explore the development noted up thread, that cars bought in recent years, seemingly by quite ordinary families, are bigger and bigger, often to the extent that they no longer fit inside the lines of an ordinary parking space.
We reluctantly came to the conclusion that the UK is a very vehicle-centric economy and that the power of the industry maintains a vice-like grip on politicians and policy to the extent that, inspite of there being clear data supporting a whole slew of changes in design and habits, nothing of any real value happens - indeed, quite the opposite.
One chum reminded us that in Tokyo, the sale of new cars is illegal unless the prospective buyer can show that they have a parking space and wondered whether that might not be a sensible step to take here in Bristol - at which point we all fell about like the robots in the Smash advert...

[Jdsk]

Thinking about the wide range of technology that's appearing in modern cars, it's quite apparent that the designers could add all sorts of ideas that would protect anybody involved in an accident who was outside the vehicle, but they choose not to. We wondered why that was the case.

Because there aren't enough countervailing pressures. And of course those aren't going to come from individual purchasers of individual vehicles and "market forces".

And one of the key building blocks of doing it better should be high quality evidence.

Jonathan

[pjclinch]

Thinking about the wide range of technology that's appearing in modern cars, it's quite apparent that the designers could add all sorts of ideas that would protect anybody involved in an accident who was outside the vehicle, but they choose not to. We wondered why that was the case.

My first guess is there's no money to be made from doing it, and potentially a lot spent.
Cars sell (I would think) on the perceived direct advantages to the driver and their passengers.

Pete.

[pjclinch]

And one of the key building blocks of doing it better should be high quality evidence.

My guess here is that your idea of "high quality evidence" is not that of the automotive industry, where I'd wager "the focus groups liked this colour most!" is more the thing than "we can be sure this will save pedestrian lives"

Pete.

[Jdsk]

And one of the key building blocks of doing it better should be high quality evidence.

My guess here is that your idea of "high quality evidence" is not that of the automotive industry, where I'd wager "the focus groups liked this colour most!" is more the thing than "we can be sure this will save pedestrian lives"

It sure is. And I don't expect the industry to do much of it on their own.

It's clearly a matter for state intervention because of harm to others, and nowadays that means it has to be a matter for cooperation between states because regulations and sales are international.

Jonathan

PS:
Euro NCAP 2025 Roadmap
https://cdn.euroncap.com/media/30700/eu ... 025-v4.pdf

... but of course that's at the vehicle level, and the bigger issues of whole system safety aren't included, and need to be addressed elsewhere.

[Mike Sales]

And one of the key building blocks of doing it better should be high quality evidence.

Jonathan

There is no high quality evidence, or even any good evidence, to justify the overwhelming prominence of helmets in the campaigns to make cyclists safer.

[Jdsk]

I expect that this thread is now destined for the Helmets safe space, and we'll lose a valuable discussion.

: - (

Jonathan

[Mike Sales]

I expect that this thread is now destined for the Helmets safe space, and we'll lose a valuable discussion.

: - (

Jonathan

Good point, but risk compensation is very relevant, I think, to helmet wearing, and road safety in general.
Is any topic in the ghetto lost, do you think? That is a pity, and perhaps shows why quaranting discussions is mistake. Surely we can keep civility here?

[Jdsk]

My experience of this forum is that introducing the topic of cycle helmets has a negative effect on the discussion of other subjects. And deters other potential contributors.

Jonathan

[Stevek76]

PS:
Euro NCAP 2025 Roadmap
https://cdn.euroncap.com/media/30700/eu ... 025-v4.pdf

The proposed pedestrian changes seem rather weak to me, good that they've recognised that torsos are actually important (!) but no acknowledgment that the way they're conducting the tests in throwing the 'pedestrian' into the car rather than the other way around isn't actually very representative.