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Comment by cperciva | Hacker News Reader

I think this is a foolish statement: fatal accidents in the US are 1.3 per 100M miles driven. Tesla reports autopilot has driven 100M miles. That's not enough data collected to draw this kind of conclusion.

Also, not all miles are equal. I'd hope that people are enabling Autopilot primarily while driving on straightish roads with good driving conditions -- in other words, at times when the rate of fatalities with a human driver is far less than 1.3 per 100M miles.

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I thought most fatalities are on the highway during good driving conditions, where the road is so smooth and boring that humans lose attention, fall asleep or staring at their phones. Speed is much higher when driving on those roads and there is a bigger chance a car will rollover/bigger impact.

At least in Germany, driving on the Autobahn is about 3x to 4x safer than driving on other road types: https://en.wikipedia.org/wiki/Autobahn#Safety, not sure how it compares to the US, but "fast and boring roads" seem to be safer.

Germany is a unsuitable country for comparison, as they have many highways without speed limits. I would argue that this invalidates the boring part.

It's the same in all European countries.

Germany is the only EU country having roads without speed limits - https://en.wikipedia.org/wiki/Speed_limit#Roads_without_spee... .

Outside of EU, the only other European location that would qualify would be Isle of Man (as referenced in that article).

I don't think the Isle of Man has any dual carriageways, it certainly doesn't have any motorways.

And one road in the Northern Territory, Australia: https://en.wikipedia.org/wiki/Speed_limits_in_Australia

I was referring to the highways being more safe than other road types.

I think the missing speed limit isn't that big of a factor, as most traffic is still flowing at around the same not-so-high speed, maybe somewhere between 130 and 160 km/h (except for trucks on the right lane). It's the relative speed differences that matters, and there the differences on other roads where traffic is stopping and accelerating all the time, with other vehicles, pedestrians and cyclists crossing the road which makes urban roads so dangerous.

Seems you have never been to Germany ;-) No offense. Most highways have a speed limit only some have none.

And most of the highways that don't have a speed limit are quite narrow so while it is possible, no sane driver would do so.

If you look at highway A5 as an example. This highway has 8 lanes, which makes driving fast quite dull since you can not really feel the speed relative to the environment.

The figure I've seen is 50% of Autobahn is without speed limit, 25% with permanent limits (due to noise control, permanently high traffic volume or intersections) and 25% with temporary limits (depending on buildings works, weather, congestion). Of course the perception is probably worse because more people use the congested parts with speed limits, and due to the limits they spend more time on those parts...

Getting a drivers license in Germany requires a lot more training (and money) than in the US. The people who do get licenses in Germany are generally better prepared. As a result, they get into less accidents.

https://en.wikipedia.org/wiki/Driving_licence_in_Germany

In the UK the motorways (straight, multi-lane, higher speed limits, barriers) are the safest roads, in terms of death or serious injury per vehicle mile. The most dangerous roads are typically single carriage A roads that are twisty, contain blind junctions and so on.

For those familiar with the UK road network see: http://roadsafetyfoundation.org/media/32639/rrm_britain_2015...

On a per mile basis, they most definitely are not. Here's one set of US DOT numbers[0] from 2007 that show the rate on interstates is 0.7/100M miles while the rate is highest on collector roads at 1.99/100M miles followed closely by local roads at 1.94/100M miles. Interstates have less than half the fatalities on a per mile basis as local roads.

[0] http://safety.fhwa.dot.gov/speedmgt/data_facts/docs/fataltbl...

Surely per mile makes no sense, as you travel faster on a motorway?

The only measure that makes sense in this context is time, bringing distance into it is statistical trickery.

Thanks for pointing this out, I was trying to figure out why my brain didn't like per mile for things moving at vastly different speeds.

When traveling, most people do so for a given distance, from hither to yon, not for a given period of time.

Again, not true, you fundamentally misunderstand the majority of car trips.

If my job is 2 hours away because there is no motorway, I will get a different job. If there is a motorway, making the commute 40mins, I will take that job.

People care how long the journey is, not how far the journey is.

People live by commute time, not commute distance. Same for service areas, if the roads all have low speed limits you would need more drivers, they wouldn't just drive for longer.

Out of curiosity, if the motorway is shut down due to an accident or construction, would you drive for 40 minutes and then pull over to the side of the road and work from there?

Personally when facing decision between highways, local roads and other means of transportation I almost always have a specific destination in mind. Accidents per mile is the statistic I want.

Accidents per hour of driving would be more useful for public policymakers – given fixed average commute 1 hour per day, what's the tradeoffs of building highways (worker mobility, commerce, pollution, landscape, accidents).

Absolutely not the case. If you're driving from A to B, you have to cover similar distance regardless of type of road. (Yeah not conpletely true.) It turns out that highways are both quicker and safer, but the two are not necessarily correlated.

That's not how it works.

If you expose yourself on a live fire range for 1 second and travel 100m/s, it's far less dangerous than exposing yourself on a live fire range for 100 seconds travelling at 1m/s.

It's the same thing with cars, the longer you are physically on the road timewise, the longer you are exposing yourself to the chance of an accident, regardless of distance travelled.

Not sure why you think it's "absolute", you haven't listed a single reason or argument, just a tautology.

The analogy is poor: on a live fire range the bullets move much more quickly than you. The speed of the bullets relative to you is largely determined by the bullets, and your speed is irrelevant - so how fast you move is naturally irrelevant (assuming random fire, of course). The chance of collision will be determined largely by the number of bullet-meters made. If you will: it's as if the bullets are exploring the space in a probabilistic/ballistic fashion - the more bullets and the faster they go, the more they can explore.

Conversely, when you hit something on the highway, it's likely to be moving much more slowly than you (e.g. the chicken crossing the road), or at a speed similar to you (the drunk guy driving on the left side). So your speed matters - you're more likely to reach that obstacle in any given period of time if you can explore more space in that time.

Correcting for time (I am making up an average speed): Highway 49.0/1Mhours @70mph Collector 99.5/1Mhours @50mph Local 77.6/1Mhours @40mph

That's not how roads work, the average speed of a road isn't simply the max speed of the road. Especially not in towns, compared to motorways, which will skew it heavily towards motorways.

I would agree that autopilot miles are not equal to overall miles. I was not able to find data on which are most risky. My guess is that most accidents happen on surface streets but most fatalities on highways.

I think most accidents are within a couple miles of home. It's so familiar people stop paying attention.

Is that most accidents, or most per mile driven? Because for many, quite a bit of driving is within a few miles from home, skewing the data.

Couple this with the fact that most people are still concentrating on the road while autopilot is in action. So in effect you still have a human driver, they are just not fully engaged with the cars controls.

I know when I tried my friend's auto-pilot that I was concentrating 10x more on the road than I would be normally. Obviously if I got more comfortable with the tech then I would be concentrating less but I can't imagine that I would ever stop paying attention unless I knew the system was fool-proof.

>most people are still concentrating on the road while autopilot is in action //

This must be harder than concentrating when you're actively engaged?

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