People often complain about the quality of cars, even before Toyota's fiasco. However, few stop to think how much more reliable and long-lasting cars are. One of the many features that is more reliable is the speedometer. We have had several cars in the last two decades that have had much more accurate speedometers than previous cars.
In the late 70s when the 55mph limit was opposed, many people gamed the system because a few court cases ruled that a driver could not be ticketed for going less than 10mph over the limit. I regularly drove my Fiat 124 Sport Coupe between southeastern Pennsylania and New York City at 70mph. Oops! That's 15mph over the limit. Not really, my actual speed was 63mph. I went right by at least one patrol car parked under a bridge while my CB crackled with a warning that there was a smokey under that bridge. It was also fun to watch those who had previously passed me slow down to less than I had been going.
When we bought our first Ford Escort I couldn't understand why so many people were passing me when I was going 55mph. I took a few measurements and discovered that I was actually going 47mph!! The dealer wouldn't do anything about it, making some noise about tire wear, blah, blah. Tire wear on a new car?? Once I began driving a true 55mph, I passed a lot of Escorts driving much slower than I was. I guess the Escorts were wearing their tires out within a few miles of the dealers.
The 1997 Ford F-150 I bought later had a much more accurate speedometer. I think it was correct within one mph at highway speeds. It did fairly well at lower speeds; I went past many a radar sign registering 30mph just like my speedometer.
Our 2002 Prius is just about as accurate.
On a recent trip we timed our Chevy Trailblazer at 70mph on a six-mile stretch of I-35W. If our speed was exactly 70mph we would have covered the six miles in 308.57 seconds. We covered the distance in 308.9 seconds, and so our speed was 69.926mph.
Of course, our measurements weren't that close because of reaction time, plus it is difficult to set cruise control right on the line on the speedometer. I think I had it slightly under, but I couldn't be positive without reading glasses.
Even that is damn good. If one were to allow a one percent error, the range of time would be slightly outside 306 to 312 seconds. That is a whole lot better than the 17 percent error of the Ford Escort or the 10 percent error of the Fiat 124.
