Am I going to slow, or are they all speeding?

Are you the one who is always being overtaken on the freeway, and wondering if they are speeding, or if you are going to slow.

Your not on your own. There are so many discrepancies in vehicle speedometers, which turns the road into a nightmare at times, particularly in high policed zones. None of us want to get fines or get more demerit points so the vast majority stick to the limit by the vehicle speedometer. Statistics show that most speedometers under-read by around 5kph at 100 kph.

So what is the law regarding speedometers and your speed?

Australian design rule

Australian standard states, that a vehicles speedometer must not indicate a speed less than the vehicles true speed, or greater than the vehicles true speed, by not greater than 10% plus 4kph. 

So what that means is that while you are travelling at 100kph by your speedometer you must be travelling at a true speed of between 87.3kph and 100kph. 

Must I follow my speedometer?

No you don’t need to follow your speedometer. The rules clearly state that you must abide by the posted speed limit for the road on which you are travelling on. How you determine your speed is up to you. You may know how far out your speedometer is and that you can travel 5kph above what the speedometer is displaying for example.

How can I check my speedometer

Roadside checking points

We have all seen the speed check points. These are most prevalent in the backstreets and flash up your speed as you travel past them. Try driving past at a steady speed. Cruise control is the best way to keep steady speed, and check the difference between the sign and your speedometer. Modern digital display speedometer’s are best for this.

Use google maps to check your speed

These days GPS accuracy is fantastic and within around 5 metres under clear sky using a smart-phone. Try traveling with google maps running which will display speed. Once again use cruise control to keep a steady speed and see how it compares to google maps speed. If google maps is displaying a steady speed you can be assured it is receiving a good signal and the speed displayed will be very accurate. 

Does it really matter

There are a few aspects to this argument, We are all entitled to be on the road, but would it be better if everyone was doing the same speed. Yes of course it would, So its all about looking after everyone on the road, so if your going to slow you are creating flow issues on our freeways.

Will I save time by doing the speed limit

Short answer is. Not really. As an example lets say you travelling without any delays and you need to travel 100km to your destination, the posted limit is 100kph.

If you sit on the true speed limit the entire journey, it will take you exactly 60 minutes

If you speedo is under-reading by 5kph and you follow that, hence your doing 95kph the entire journey will take you 63.5 minutes. 3.5 minutes longer.

Conclusion

So the reality is that you may be the one with the dodgy speedometer so to speak, despite it being within Australian standard which gives very generous error range. So its a matter of choice how you determine speed. Myself i would like to see everyone doing the same speed to avoid so many lane changes which are the cause of so many accidents. All we need to do is drive with respect and defensively at all times as humans do make mistakes.