They technically don't in a meaningful sense.
What they do is make a car that has high torque and can accelerate 0-60 mph as quickly as possible. This has the unwanted side effect of also being able to still continue accelerating quickly past the target zone (<= 85mph). Some street legal cars have governors because of how exceptional their acceleration is.
The acceleration in cars are designed around pretty much one extra horrible edge case: accelerating up to freeway speeds, up an onramp that is entirely too steep (yet legally designed), from a standstill (ie, gridlock conditions), while also carrying max cargo capacity. Cars must be able to do this to be considered safe by any meaningful definition.
Also, there are no laws against going fast. The laws are purely against the law on public roads, as per the posted limit; there are many private racetracks that are completely legal. Not all countries even have limits comparable to America's, so being able to safely go 100+ mph is worth it if you were to, say, drive on the German Autobahn.
And electric car motors can draw almost maximum Amperes at very low rpms, hence the insane numbers of torque for electric cars
Most manufacturer limits on top speed are tied to the vehicle tire speed rating (usually somewhere around 92-116mph). There are a few that are sort of an industry standard cutoff for 'safety', like 300kpm (I think) on sport bikes.
Since this meme comes up a lot: About two thirds of the Autobahn network do have speed limits, ranging between 80-130 km/h (50-80 mph). In fact, one of the arguments for a general 130 km/h speed limit is that it would reduce the rate of speed limit changes, thus making traffic flow smoother overall.
But we could rephrase it to "why aren't top speeds limited to the maximum speed limit?".
It's got me thinking about the creeping culture of safetyism, especially against the current backdrop of Covid-related restrictions.
In some ways it makes no sense that cars are not restricted to a sensible top speed. Either a simple dumb limiter set to the top speed limit for the country, or something more sophisticated using GPS (or a combination of the two). Doing so would possibly (probably?) save many lives per year. Yet it's unlikely to happen because:
1. there's a powerful automotive industry that relies on cars retaining their power as a status symbol
2. there are a lot of powerful and influential people who enjoy driving fast cars.
It frightens me that we are seemingly only able to retain our freedoms when there is some powerful industrial lobby to protect them.
People are currently being subjected to much, much greater restrictions of freedom than having the top speed of their car capped. Entire livelihoods are being destroyed on the basis of "saving lives". Perhaps this is justified. I personally don't think so but a convincing argument can be made.
If there's a conclusion to this, it's that we need to move past the "if it saves some lives, it's worth it" style of argument.
It sounds brutal, but some values are worth holding on to even if they kill people. You may balk at that statement, but you implicitly accept that compromise every day, even if you've never explicitly thought about it.
Places that have some roads with unrestricted speed probably wouldn't be a candidate for non-GPS blanket restrictions (Germany has the autobahn, Montana has/had some roads posted as 'reasonable speed').
There is also the argument against both types of restrictions that some situations can warrant excess speeds. If you are speeding to a hospital because your neighbor has potentially life threatening injuries from being run over by a tractor, most states have a clause that allows you to break the laws to avoid greater harm in situations like this.
The best answer I know of so far is to increase driver test requirements in the US. Many European countries have more stringent testing with lower fatalities per million miles, even when comparing US interstates to the German autobahn. The number of drivers I witness who make bad decisions or don't know the law is quite high.
Most cars have a gaz engine and the efficiency of a gaz engine is not linear. To simplify, an engine often has its best efficiency around 2000rpm and can rotate as fast as 6500rpm but it will then waste a lot of energy, mostly in heat. You want the engine to operate at its best efficiency when you drive normally. So you design the gearbox accordingly, to get 2000rpm at 130km/h for example. But the engine can rotate faster, and therefore you can drive faster than the speed limit.
You can limit how fast the engines rotates, most engines do have a limit around 6500rpm, but if you limit the rotation speed, the cars will lack a lot of power. The power is the torque of the engine (how strong it can rotate) multiplied by the rotation speed. So limiting the rotation speed is quite a problem. Many people prefer to buy powerful cars. They don't even know about the torque.
You could limit how fast the engine rotates once you reach the speed limit, but for a long time this kind of technology was quite complex and expensive. Nowadays, since maybe 25 years, it's totally fine and cheap to do so. Some German brands put an electronic at 250km/h on their fast cars for example.
With electric cars it's another story and while most don't go very fast, mine goes up to 150km/h for example, some are fast only to sell them to people who want fast cars.
Today we could definitely put a limit at the legal speed limit, based on GPS and map data and for example, but many people would complain and some would buy a car without the limit. I think the only solution is to force all the constructors to do implement a speed limit at the same time.
Not to mention the extra power goes towards faster acceleration, not just top speed. The same force that gets you an extra 10mph top speed also works to get you from from 0-60mph that much faster.
It's 28 year old males with money and no sense of self-worth. There are regularly reports of people doing nothing but driving up and down a nice street downtown. Flooring it from red light to red light, dropping the clutch on every gear change. All. Day.
The completely unrelated question I would like to ask is "Why is it allowed to show your middle finger to random people on the street, but as soon as they're in a car, it's a crime?"
A general speed limit on the Autobahn is long overdue. Lots of our neighbours (see Austria, Switzerland, Netherlands, Italy) are doing fine that way.
Fossil cars are also more efficient at lower RPMs. Designing the gears such that they can cruise at highway speeds with low RPMs incidentally allows the cars to go way past speed limits as well, if they have enough extra power.
The European Transport Safety Council (ETSC), the body which supports the introduction of ISAs, says the limiters would reduce collisions by 30%, and save around 25,000 lives within 15 years.
I think this is a really brave move by the EU, and a great example of use of technology to save human lives. I wonder if these kinds of "unpopular" legislations are rarely be made by local governments filled with politicians up for re-election every four years as it spells doom for chances re-election.
1. https://www.europarl.europa.eu/news/en/press-room/20190410IP...
2. https://www.rac.co.uk/drive/news/motoring-news/mandatory-spe...
A speed limiter is a feature that prevents a vehicle from doing something that many potential buyers want it to be able to do. There's absolutely no incentive to build in one that can't be disabled. In contrast, ones that can be optionally enabled are common - my car has such a feature, and I often enable it for sections of road with average speed checks.
That said I generally stick to the speed limits [1], but what if I need to get to the hospital in a hurry? At least around here local laws are quite clear that you are allowed to break laws and regulations to save lives.
[1]: old habit, wasn't always a well paid programmer and also I mostly think it is the right thing to do :-)
What history, politics and leadership classes at school (as well as following the news for a couple of decades afterwards) has told me is that such tools should be used to protect ordinary citizens against abuse of power, not to simplify the lives of those in power.
Otherwise we should just as well make it mandatory that everyone wears GPS trackers and has cameras installed in their living rooms as that should certainly reduce unsolved crimes ;-)
(To make it clear: I support the police, at least our local police, but I still think they should be logged whenever they do something at work that ordinary citizens aren't allowed to while ordinary citizens - and off duty cops for that matter - should only be logged after a judge has allowed it for the investigation of a specific case.)
Edit:
A very practical example: 3 kilometers down the road next to me there is work going on, so instead of 80 km/h the limit is 30km/h.
All well and good except the speed limit doesn't stop until a few hundred meters after the roadworks. Almost everyone breaks the speed limit here, or can we just accept that sometimes people have good reasons for breaking the rules?
Do we want all that information in the hands of already powerful people so that they can selectively enforce it against their enemies? (admittedly less of a problem here in Norway, but you catch my drift).
Driving a car that doesn't accelerate well while hearing a sound like you are hurting your engine is unpleasant, even for passengers.
* Passing someone slowly is extremely unsafe
* Sometimes evasive maneuvers require accelerating rather than braking to avoid danger
It's all about the car - don't drive 260 in an Octavia, not even a Passat, much less a second-hand one. Recent Mercedes E-class with all the additional safety equipment can handle high speed crashes well, and the automated systems can do a lot for prevention as well as saving the situation (but there aren't many situations that need saving with the prevention systems).
BTW going 260 in a Mercedes feels about as controlled and smooth as going 70 with less expensive cars. It really is something totally different, and you have to feel it to truly understand it.
2) Speed limits change. It would be a hassle (understatement of the week) to update every single car.
3) As others have said, you can always drive legally on private tracks.
Acceleration is a big part of the enjoyment of fast cars. That's not usually illegal.
Also, having better acceleration can help reduce the 'time exposed to danger' when overtaking, which may still be below the local speed limit. Faster cars can be safer, see...
Acceleration is definitely helpful (to a point , even on the track), but for instance I live in the UK where the max speed limit is 70mph, and my very ordinary car is specced to do more than double that. I don’t see the benefit of being about to do >>100mph outweighing the risks- earlier comment mentions how this arises from the need for useful torque bands in IC engines which explains a lot and makes perfect sense, but with modern engine controllers and especially electric I agree that this is no longer necessary to leave enabled in the vast majority of vehicles.
Because people are willing to buy them.
It also supports typical human behavior. If you're neighbor has a 400hp car, to "one up" them you buy a 500hp car.
Childish? Yes. Are adults with childish behavior new to the human race? Not at all :)
Now you could attempt to give a fair answer why you think this is hard to implement correctly or why is a bad idea.
Also we could theoretically install something that can detect if the driver is tired,drunk or not paying attention. There is no requirement that police or government must be involved , maybe in some countries you can implement and solve this with free market , insurance and all that good capitalistic/freedom stuff.
Drivers sometimes hit other vehicles. Airbags go a long way here. Sadly, drivers will often hit less fortunate road users such as pedestrians and cyclists.
We already know that pedestrians hit at 30 km/h vs. 50 km/h stand a much better chance to survive. Sadly, cities are rarely designed for 30, and usually more 50+, depending on the city.
Changing cities is, well, possible, but also kind of difficult and unpopular. You know what's easier? Making car manufacturers limit cars' speeds in cities.
It's not technologically difficult. Lots of new cars already read speed signs. Almost all of them have some sort of GPS component.
Geofencing speed limits seems like a pretty easy fix compared to the infrastructure changes of traffic calming (which we should do anyway). You can make it opt-out (and non-trivial enough to do so) so that most new cars on the road have these limits at least in cities.
Does this sound crazy? I'd argue it isn't. Consider that E-bikes/E-scooters are limited to 25km/h in a lot of countries. Similar story with small 50cc scooters. In some places rental E-scooters even have geofenced speed limits already, and the Netherlands is considering a similar plan for E-bikes (ones owned by ordinary citizens).
Where does a city begin? End?
Should we cover the suburbs with the geofence?
What about the beltways or highways that go through the city?
In big cities, GPS is spotty or completely unavailable, what do we do there?
What about city streets which pass under/over highways?
As I've pointed out in other replies, there isn't a good enough, when forcing cars to slow down significantly. Road conditions and surrounding traffic speeds make any unexpected slowdowns ripe for creating accidents.
I don't quite know what your (American?) suburbs look like, but in theory I don't see why not in this instance.
And if you're concerned about, idk, people not being able to get to the hospital on time or what have you, make them opt-out on every single ignition. Most people will probably not be bothered to opt-out every single time.
As for the technical points regarding GPS, lots of cars already read speed signs and come with various computer vision based safety features.
Again, ebikes and escooters are already speed limited and geofenced. It's not perfect, but why aren't we so concerned about ebikes being slow and not being able to keep up with cars and subsequently be hit by them?
Lastly - it doesn't have to come into full effect if you're at 120km/h. You can be smart about it, like not slowing you down but not letting you accelerate, easing you into the speed limit etc.
There's a perception that cars are a fact of life and it's OK for them to be traveling at speed in cities, whereas the reality is that in most urban areas we simply cannot afford to keep this up any longer.
