Which is more accurate, the speed shown on a speedometer or a sat nav?

On the occasions I use my smartphone as a sat nav, I get a readout of the speed of the car on the screen. It always shows a slower speed than my speedometer by 3-4mph. Since this can make all the difference in some areas where they have speed cameras set to catch drivers going above 20 mph, would you regard the smartphone figure as a more accurate and reliable guide to avoid being caught out?

Asked on 16 March 2020 by Neil Littman

Answered by Georgia Petrie
The sat nav on your smartphone is more accurate, speedos generally read a little over what you're actually doing.
Tags: speedometer
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