The answer is: marketing (as such, this isn't really a UX question)

Is it possible that it's easier to read the speedometer, for either physical or psychological reasons, within a smaller portion of the circle?

It may be rare for you to go more than 100 mph, but you are not everyone. There are people who occasionally drive that fast. Also, how many cars still have retro dial-like speedometers, rather than digital displays?

@jamesqf those people aren't driving the Toyota Camry I was driving when I thought to ask this question. And many/most new cars I see still have dials.

@jamesqf - there are also people that occasionally shoplift items from stores, but that doesn't mean that clothing manufacturers should put hidden pockets in clothing to make it easier for them. Sure, there are a few people that legally drive stock cars over 100mph on private roads or tracks -- I have some friends that are amateur racers and they all have after-market gauges on their cars that could be used to show speeds > 100mph.

@Johnny: I can't quite see how you can equate shoplifting with driving over 100 mph.

@jamesqf Because they are both against the law? (at least in the USA -- the maximum speed limit of any state is 80mph)

The Honda Accord (at least the 2014 models) has an almost entirely digital dash (save the tachometer). Digital speedometer and instant fuel efficiency. If you press and hold the button on the upper right of the tachometer, you can switch between mph (and mpg) and km/h (and L/100km)

You should also consider track days, which are legal even in the US en.wikipedia.org/wiki/Track_day Not that you will enjoy much of it on a Toyota Camry, but one never knows :-)

I've always wished for a speedometer dial that is very spaced out at the lower end and becomes more compressed towards the high end. That way you can have both: good readability at those speeds used 95% of the time, but also coverage of the entire range of speeds the car is capable of.

From a european / german / science point of view this question is just so 'great' – and a bit 'strange' maybe. A speedometer still just measures the speed of the car – that's physics – and that has basicall nothing to do with whatever speed limit there might be.

@tillinberlin I'm not asking about speed limits, I'm just asking about driving speed in general.

The same reason Nigel Tufnel’s amp goes up to 11 in “This is Spinal Tap.” But that isn’t a perfect analogy since the amp really is just a measure of scale in volume. But the concept is the same: Car purchasing and usage is sometimes more psychological than it is practical. And cars that can go faster than the legal limit appeal to many people’s competitive nature. Period.

@romkyns my 2001 Vauxhall (= Opel) Astra had a speedo that was more compressed at the high end; no other car I've ever driven has had. It also set the dashboard clock automatically from the RDS radio signal, again I've never found another car with this handy feature. However the diff failed before it reached the 100 000 mile mark :-P

@ssdecontrol I know – I just wanted to point out that the speedometer measures some data from a machine – in this case the possible speed of driving – no matter what personal preferences the driver has, be there speed limits or not. Of course there is always some additional / potential figures. That's because manufacturers mostly only have one type of speedometer for all cats of one branch – no matter what engine the car has. It's a bit like the scales on medical thermometers that also go to rediculous numbers no patient would survive..

The original reason was accuracy/liability afaik. Current reasons will vary.