Why speedometers go to 140 or 160 mph, even if cars can't drive that fast

• Most speedometers max out around 140 or 160 mph, even though the cars aren't designed to go that fast.
• The practice serves automakers' needs to mass-produce standard gauges for different cars.
• It also adds psychological benefits to drivers, who may want to think of themselves as amateur racecar drivers.
• The downside is people may feel too powerful in their car and drive recklessly fast.

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Most of us don't own a Bugatti Chiron, a supercar whose speedometer maxes out around 300 mph. Chances are, the minivan or sedan in your driveway only purports to go 140 or 160 mph.

But even if you floor that family roadster, you're unlikely to top out much above 100, leaving a whole swath of unused real estate on your speedometer at the 120, 140, and (if your car talks serious game) the 160 mark.

From a design perspective, this makes little sense: Why bother making a gauge that doesn't accurately reflect the car's true capabilities? Turns out the answer is slightly more complicated.

Speedometers are made to fit a range of cars

Logistically, automakers can't make a new gauge for every car. Given the cost of doing so, they wouldn't want to either. So in an effort to streamline the process of making speedometers, many will use the same gauges for their mid-performance vehicles as for their higher-end models.

The practice also reflects the manufacturers' need to sell internationally. Cars that travel mostly on roads without speed limits - say, the German Autobahn - need some extra room on the dash if the car's performance will match the road the car travels on most, Kurt Tesnow, who oversees speedometer and instrument clusters for General Motors, told the Associated Press.

Higher gauges make dull cars seem sporty

Even if some manufacturers don't necessarily need to use the same gauge across their various lines, they still have a vested interest in appealing to people's need for speed.

"People really want to see higher numbers," Fawaz Baltaji, business development manager for Yazaki North America, a large supplier of speedometers to auto companies, told the AP. "It is indicative of a more powerful engine. There's a marketing pitch to it."

Regulatory agencies have tried to redesign speedometers over the years, mostly to no avail.

In 1974, President Nixon created a national speed limit of 55 mph. (In older cars, you can still see a red line at 55, for just that reason.) In 1979, the head of the National Highway Safety Administration enacted a rule prohibiting gauges from going above 85 mph. President Reagan overturned the rule two years later, and manufacturers quickly got back to making 120 the top speed.

There are other benefits (and drawbacks), too

There does seem to be a psychological benefit to having speedometers far exceed the normal driving habits of most drivers, according to Stewart Reed, chair of the Transportation Design Department at ArtCenter College of Design.

If the gauge topped out at 80 mph, highway driving would push the needle all the way to the edge, which could induce some degree of concern. But if it topped out at 140, the line would stay mostly vertical on the gauge, in what's known as "top dead center." It would seem further from the car's peak performance, and therefore safer.

"It could be that the speedometer, at a certain position relative to other things, is kind of a natural highway cruise position," Reed told Business Insider. "And the rest is just numbers."

Of course, if those numbers are so high that drivers start believing they can handle high speeds, they may drive more recklessly. Suddenly, a used Honda Civic starts to look a bit more like that Bugatti - for better or worse.