I’m probably going to open up a whole can of worms here, but your car speedometer, some of the time, isn’t right. For the most part, it only needs to be accurate to within plus or minus 5 mph at 50 mph. Here in the UK the law is slightly different, allowing speedometers to be displaying a speed which 1-6 mph faster than your actual speed.
Due to the laws here and in other countries, most manufacturers seem to stay safe and calibrate speedometers to show a speed which is faster than you’re really going – by about 3-4 mph.
So, if you’ve ever had a TomTom or you’ve used a speedometer app on your phone, you’ll notice that sometimes it shows your doing 50mph but your speedo is show 53 or 54mph.
Then, of course, you have to work tyre sizes into the equation. If you’ve taken 16″ alloys off your car and put 18″ alloys on, your car is going to go a bit faster.
Anyways… so, you’re in the average speed camera section on the motorway. You’re welded to 70mph, but are you really doing 70? Well, if you’re using Google Maps you can now show a speedometer. Sure, it’s been available in other apps for a bit, but I tend to default to Google Maps when I’m navigating anywhere.
To get the speedometer, head to Settings -> Navigation Settings. In there, if you scroll down, you’ll find “Speedometer”. This will tell you the speed as judged by those magical satellites and how fast your position is changing.
Boom! Now you can compare speed.