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Comment by oldgradstudent | Hacker News Reader

It's a weird piece. The describe the XC90 as the safest car they ever tested, and that it hadn't had a fatality since 2002. Then it attributes it to AEB.

The problem is that the XC90 got its AEB in 2015. This cannot be the reason for the impressive safety levels since 2002.

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Yeah. The Volvo XC90 is a big car and most of the excellent safety record for it can be attributed to the inherent higher safety of larger cars:

https://www.edmunds.com/car-safety/are-smaller-cars-as-safe-...

https://www.technologyreview.com/s/413018/laws-of-physics-pe...

It's just physics. When large a object meets a small object then the large object wins because it has more energy and ends up pushing the small object backwards.

Also the fact that it's a Volvo, which among other things will introduce a lot of selection bias. For several years, there were no deaths in a Volvo 240 either:

http://community.seattletimes.nwsource.com/archive/?date=199...

Fatalities are quite rare. 2011-era midsize luxury SUVs have 13-15[1] driver deaths per million registered vehicle years in the US (UK has half the death rate per km, vehicle or inhabitants).

It is not that improbable that midsize luxury SUV that sold just 50,000 cars in the UK since 2002 had no driver deaths.

AEB was first installed in the 2015 model year. If we assume[2] that the same number of cars were sold each year, the XC90 had 20,000 registered vehicle years with AEB. We should expect 0.03 deaths.

It would be more surprising if there was a driver death in a Volvo XC90 equipped with AEB in the UK.

[1] http://www.iihs.org/iihs/sr/statusreport/article/50/1/1 (first table)

[2] It's probably false, adjust with your favorite fudge factor.

Also, surely that needs to be more accurately described as 'safest car ever tested /for its occupants/'.

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