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Comment by badcppdev | Hacker News Reader

I think it's really funny how humans can't help but use round numbers.

30 kph = 18.64 mph

20 mph = 32.19 kph

So safety rules around the world are based on arbitrary length systems. I'm all for lower speed limits for safety but I feel there is still things to be worked out in suburban settings where long arterial(?) roads carry large amounts of traffic in large cities.

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2 km/h when you're reducing from 50 to 30 is a negligible difference, and round numbers are easier to keep to on analog/digital speed gauges, and easier to set manually on cruise control systems

It's not like anyone ever drives exactly that speed anyway. It's all approximations. We don't need 4 digits of precision here.

What do you mean, one system is SI units and other is, ehm how to put it kindly, weird for weird people.

That 'roundness' can be a pain. E-bikes are generally limited to an arbitrary 25kph (eu) - 5kph slower than a car at 30. Constantly in the way...it's one of two negatives I have regarding e-bikes: too slow for traffic, too fast for pedestrians/ shared paths.

It’s almost as if it’s based on what can be easily gleaned from a speedometer on the dashboard.

It is just that Americans are tougher people. That's why during the height of covid, Americans could safely stand 1.829 meters from each other without getting infected while the rest of the world required 6.5616 ft for the same level of safety.

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