Vehicle capabilities are separate from driver responsibility. Nothing would be possible if we banned things just because they have the potential for harm.

Why is it such a bad idea to just fit in speed limiters and be done with it?

And that last part? It's pretty much an empty argument, as if we don't already regulate/restrict/ban many things with the potential to cause harm (cars included).

Beyond that it's not necessary because most people follow the law. The same irresponsible people who speed like crazy would also remove the speed limiter. Also there are general driving conditions, emergencies, private roads, and other situations where people use the full capability of their vehicles. And police are still need to patrol the roads for more than just speeding.

Overall a built-in speed limiter just limits freedom, costs more resources and enforcement, punishes responsible owners, and prevents them from enjoying their vehicles because of a tiny percentage of bad drivers. In fact Germany's autobahn with completely unrestricted speeds has a better safety record than other freeways which shows that fast cars at high speed are not the issue at all for safety.

do you also want to ban usain bolt from the sidewalk because he could run too fast if he wanted to?

And how do you plan to get up to that speed? If you’re going to use something with motorised assistance, it will almost certainly be a device that the State will class as a road vehicle. Driving on the sidewalk is illegal.

Any "limit in practice" is not a prescribed limit. The whole point of posted, visible speed limits is that everyone knows what they are ahead of time. They're not a substitute for using your brain.

(Also in practice if you go too fast you'll run up against physics and literally burn up due to atmospheric drag.)

> And how do you plan to get up to that speed?

OP's example is a world-class track sprinter. Usain Bolt just runs fast (for 100-400m).

In my state, non-motorized bicycles may use the sidewalk freely. When riding on the sidewalk, cyclists are considered pedestrians. They (like all other pedestrians) must be courteous to other pedestrians, but there is no speed limit.

In theory, on a long enough sidewalk without ramps, alleys, obstructions, etc, a cyclist could plausibly exceed 30 mph without being discourteous to anyone or endangering others. There are some sidewalks like this in the industrial parts of my town, although I'm certainly not suggesting anyone try it.

I don't understand the point of stating the blindingly obvious as though it could serve as a useful retort. Obviously there isn't a prescribed limit. That doesn't elide the point—a limit doesn't need to be a bright line in order to exist in practice.

My argument is wrong because it is silly. Gotcha.

>do you also want to ban usain bolt from the sidewalk

When Usain Bolt can delete a family from existence with one wrong flick of the wrist, I'll support banning Usain Bolt from running in the sidewalk.

Alternatively, when Usain Bolts running in sidewalks are one of the leading worldwide causes of death.

And I'm pretty sure that if Usain Bolt were running at 30kph on a crowded sidewalk somebody would stop him, which is actually a pretty nice analogy to the obviously beneficial measure of placing a speed limiter on cars.

No, it's so wrong that it is silly. That wasn't supposed to be the reason why.

Stop looking for cheap gotchas.

Because they meet all of the legal requirements to be operated on public roads.

FYI, I think this new car is estimated at over 500kph max speed.