Back in October, Andrew from High Riser wrote about the Australian Design Rules. I replied with the following comment.
I will like to mention the most hilarious of the Australian Design Rules – that vehicles may not under-read the speed, but may over-read the speed by anything up to 10% + 4 km/h
This means that if your vehicle’s *actual* speed is 100kmh, the displayed speed is permitted to be anywhere between 100kmh and 114kmh!
I have tested my Volkswagen Polo via several different means, and it is out by 10%. EG at 110km/hr on the speedo, my actual true speed is 100km/hr. Now that I know this, I can drive accordingly. To do 60, I need to do 66. To do 80, I need to do 88. It could be worse, it could be the full 10% *plus* 4km/hr, and I’d forever be doing maths in my car. And I failed maths, quite badly. :)
However, there are a whole bunch of people out there who do not know this, and many of them believe their speedo is supposed to be accurate! These people are likely wondering why people keep overtaking them when they *think* they are doing the speed limit, but they are actually doing less than the speed limit and in the case of 100km/hr, they may be doing less than 90 as a surprise to themselves.
Since making that comment, recently a discussion was held on this topic community Facebook group that I belonged to after someone posted that they were driving at the speed limit and continually being overtaken. Another group member raised the Australian Design Rules and advised the someone to do some tests on their speedo. Theirs was out the full 10% plus 4km/hr.
So, this is my heads up to you. Test your speedometer. There are many smart phone apps you can get to do this. Plus, if you are using a satnav, this will often give you an accurate true speed.