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How well do cars do in crash tests they're not optimized for?

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Re: How well do cars do in crash tests they're not optimized for?

#271

Post by kelnos »

alistairSH wrote: post #200
henryfjordan wrote: post #85

Earlier quoted context omitted.

VW actively detected if the car was on a treadmill testing setup and electronically changed the engine parameters to make it run cleaner. The water heater was designed with the test in mind but functions the same regardless. VW was clearly cheating whereas the water heater is taking advantage of known deficiencies in the test (is that cheating?).

I'm not sure that's an accurate description of VW's cheat. VW knew the parameters of the test (stationary car, no steering input, prescribed throttle inputs, etc). And they configured the car to pass the test. Water-heater engineer knew the parameters of the test (number and location of probes). And he configure the water-heater to pass the test. Same-same. In both cases, an engineering team willfully committed fraud…

It's not the same at all, and I don't think the differences are pedantic.

The water heater runs the same regardless of whether it's being tested or is running normally in someone's home. Really, this test "cheat" exposed that the test itself was not measuring what it thought it was measuring; and hell, a manufacturer could accidentally cheat with their design.

The car would run differently if it detected it was in a test situation. In the real world, with a real driver, it would run in a way that would give different test results (if you were in a position to run the test while it's being driven).

Re: How well do cars do in crash tests they're not optimized for?

#272

Post by throwaway0a5e »

gav wrote: post #126
kube-system wrote: post #59

Earlier quoted context omitted.

The person is not suggesting it's a statistical flaw -- but that it's a self-selection bias. Hypothesis: The people who opt to spend more for a 4wd version are people who know they will use it because they operate the vehicle in inclement conditions, and/or they are uncomfortable with their ability to operate a 2wd vehicle in those conditions and/or they do not have the option to stay home when the weather is bad.

Living in Vermont for five years taught me that while a 4wd is a better choice for bad conditions, it's because they are less likely to get stuck with spinning wheels, but they don't stop any faster than a 2wd. I would see way more SUVs in ditches than sedans. People tend to overestimate what their 4wd is going to do for them and aren't sufficiently cautious. The first snow/ice of the year was particularly bad.

> People tend to overestimate what their 4wd is going to do for them and aren't sufficiently cautious.

Or because when it snows the ones who can afford to do so take the "winter beater" 2002 Trailblazer instead of the car they usually drive.

Re: How well do cars do in crash tests they're not optimized for?

#273

Post by adwww »

hansvm wrote: post #131
fractionalhare wrote: post #110

Earlier quoted context omitted.

Is that a typo, or do you teally mean cycling and walking are significantly worse than traveling by car? Are both of those activities actually more dangerous? I would have thought cycling and walking - even in urban settings! - are safer activities than driving, statistically.

I doubt it was a typo. As a ballpark, cycling has 10x the deaths per mile as driving. Here in the Bay nobody stops at stop signs (3-10mph is typical), and they don't even really slow down to look both ways till after the white line and after the sign -- plowing straight into sidsewalks and bike lanes. I'm honestly shocked it doesn't cause more deaths. Cyclists themselves usually aren't much better -- not even botheri…

There was a study on UK cycle commute accidents recently.

Commuters over several years who cycled, were 44% more likely to be hospitalised than other commuters.

However...! This cycling was associated with some quite dramatic health benefits. If 1000 people switched to cycling... The benefit would be 15 fewer cancers, four fewer heart attacks or stroke and three fewer deaths.

https://www.bmj.com/content/368/bmj.m336

Re: How well do cars do in crash tests they're not optimized for?

#274

Post by kelnos »

ebg13 wrote: post #99
ivanbakel wrote: post #93

Earlier quoted context omitted.

What was more heinous about the VW case IIRC is that the cleanliness gains the cars made on the treadmill setup were enough to push them into compliance with regulations, which the engines normally didn't meet. "Cheating" a better efficiency rating is significantly less reprehensible than cheating a legal obligation which was legislated for public health and environmental reasons.

But the efficiency ratings also exist for public health and environmental reasons. Why does it matter to you that one is a mandate? They're both intentionally deceiving regulators and consumers (vs accidentally acing the test without cheating). Both are fraud.

The difference is that the water heater test itself was flawed in that it depended on arbitrary design decisions that have nothing to do with efficiency. Two completely innocent manufacturers could build water heaters with the exact same real-world efficiency, but score fairly differently on the efficiency ratings just due to how they're designed.

While I agree that this particular water heater manufacturer was doing something shady in order to get the best score, at least they weren't selling a product that did something differently while under test conditions vs. in real-world usage. They merely realized that the test itself had wide error bars, and designed their heater to "err" in the positive side of those.

VW, in contrast, sold a product that lied to the testers about its emissions in order to pass certifications, while in real-world driving would behave in a way that would not pass muster.

And to me I think that's the key: VW's cars intentionally behaved differently depending on if they were being tested or if they were being driven in normal real-world usage. This water heater behaved the same regardless of whether it was being tested or was heating water in someone's home.

In a way I think of this in academic terms. The water heater manufacturer studied the SAT to learn what kind of questions were going to be asked. VW stole the answer key to the test and memorized it.

Re: How well do cars do in crash tests they're not optimized for?

#275

Post by kelnos »

rconti wrote: post #205
PeterisP wrote: post #158

Earlier quoted context omitted.

Transportation safety is generally measured on a distance basis. If you compare one hour of driving vs one hour of walking, then walking is safer, but if you compare the traffic risks of driving a hundred miles and walking a hundred miles, then that's a different story.

This is also kind of silly; the average person doesn't walk 100 miles (say, a week). Extrapolating relative walking safety from 100ft of darting from your office building, across the street, to your lunch spot, out to 100 miles is not actually the same thing as (say) commuting by foot 5 miles each way for 10 days (where the per-step risk profile is probably a lot lower than the numbers we're extrapolating from).

Yeah, agreed. I think you just need to be making apples-to-apples comparisons based on the type of trip.

If you're talking about trips of no more than a few miles (that don't include hauling too much cargo to carry), you can compare driving with walking. If you're talking about trips of tens or hundreds or thousands of miles, you have to compare driving with flying or taking a train.

I would be interested to see crash/injury/fatality stats for car trips under certain distance thresholds. I wonder if those are tracked anywhere.

Re: How well do cars do in crash tests they're not optimized for?

#276

Post by kube-system »

coding123 wrote: post #253
kube-system wrote: post #90

Earlier quoted context omitted.

The big difference with VW is that they put in a mechanism that detects the test and completely changed the behavior of the car for the test.

That sounds exactly like the third sentence of the article. > Sun managed to increase its score on 179.art (a sub-benchmark of specfp) by 12x with a compiler tweak that essentially re-wrote the benchmark kernel.

Sort of, except that emissions testing is a regulatory requirement.

Re: How well do cars do in crash tests they're not optimized for?

#277

Post by jariel »

On page 3 of [1] from the article which shows most number of deaths, it seems like there's almost a perfect correlation between 'size' and 'deaths'.

I remember thinking about getting a mini Cooper, literally while driving in my family's quite large SUV, and my father indicating how they are unsafe due to size. I couldn't help thinking of the odd kind of 'race to size-safety' factor severely limiting people's ability to drive smaller, more efficient cars.

I want to drive a small car for a variety of reasons. But the moment I have children ... 'safety' might be my #1 concern (along with the convenience of a large utility vehicle). It could very well be that this 'safety arms race' is harmful.

[1] https://www.iihs.org/api/datastoredocument/status-report/pdf...

Re: How well do cars do in crash tests they're not optimized for?

#278

Post by nwallin »

alistairSH wrote: post #200
henryfjordan wrote: post #85

Earlier quoted context omitted.

VW actively detected if the car was on a treadmill testing setup and electronically changed the engine parameters to make it run cleaner. The water heater was designed with the test in mind but functions the same regardless. VW was clearly cheating whereas the water heater is taking advantage of known deficiencies in the test (is that cheating?).

I'm not sure that's an accurate description of VW's cheat. VW knew the parameters of the test (stationary car, no steering input, prescribed throttle inputs, etc). And they configured the car to pass the test. Water-heater engineer knew the parameters of the test (number and location of probes). And he configure the water-heater to pass the test. Same-same. In both cases, an engineering team willfully committed fraud…

The differences are not pedantic at all. The differences are extremely significant.

The VW engineers designed the car to do different thing while being tested vs used by consumers. While being tested, the emissions system was on. While being used by consumers, the emission system was entirely disabled.

The water heater engineers designed the water heater to do the same thing while being tested vs used by consumers.

If the water heater engineers designed the water heater to never turn on and keep the water at room temperature while being tested, ("works good boss, water heater efficiency is infinity percent") then yes, it would be reasonable to claim they did essentially the same thing.

Re: How well do cars do in crash tests they're not optimized for?

#279

Post by nwallin »

coding123 wrote: post #253
kube-system wrote: post #90

Earlier quoted context omitted.

The big difference with VW is that they put in a mechanism that detects the test and completely changed the behavior of the car for the test.

That sounds exactly like the third sentence of the article. > Sun managed to increase its score on 179.art (a sub-benchmark of specfp) by 12x with a compiler tweak that essentially re-wrote the benchmark kernel.

Yes, but you're talking about what VW did vs what Sun did, but the person you're replying to is talking about what VW vs what a company that makes a water heater does.

I agree that what Sun did is very similar to what VW did, with the exception that VW's increased emissions (statistically speaking) killed people, and what Sun did likely had no health impact on anybody except a few hurt paychecks.

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