01/09/2026
I came across this question on a learner forum and it really stood out to me because I suspect plenty of learners have had exactly the same confusion.
The learner was practising with a friend and became stressed because the road signs appeared to show 30mph while the sat nav was showing 20mph. Cars were passing them, the speed limits seemed to be changing quickly and they were left worrying that something like this could make them fail their test.
So let’s clear up the first bit.
The road signs tell you the legal speed limit.
Your sat nav does not.
Sat nav speed information can be useful, but it can also be wrong or out of date.
Roads change.
Limits change.
Databases don’t always catch up immediately.
This is also a perfect example of why I strongly encourage private practice alongside professional driving lessons, rather than seeing one as a replacement for the other.
Private practice is brilliant. The more varied, good quality experience a learner gets, the better. A parent, partner or friend can give somebody valuable hours behind the wheel and help them practise skills they have already been taught.
An Approved Driving Instructor brings something different to that passenger seat.
We are trained to teach you how to identify the speed limit when the answer isn’t immediately obvious. We teach you where a new limit begins, what signs and road markings mean, how street lighting can be relevant, how to recognise the characteristics of different roads, how to plan for changing limits and, importantly, how to work things out independently when technology is telling you something different.
If you were sitting beside me saying, “The sat nav says 20 but I think this road is 30,” I wouldn’t want you to simply believe me when I told you the answer.
I’d want you to understand how YOU can establish the answer.
What signs have you seen?
What was the last speed limit sign you passed?
Has anything legally changed that limit?
What information is the road itself giving you?
Could the sat nav information be outdated?
That is teaching somebody to drive rather than teaching somebody to follow instructions.
There is another important point. The speed limit is the maximum permitted speed, not an instruction to reach it.
A 30mph road doesn’t automatically mean 30mph is appropriate at that moment.
Conditions, visibility, pedestrians, parked vehicles, bends and hazards may mean a lower speed is necessary.
This is why I love private practice when it is used properly.
Your instructor gives you the knowledge, understanding and strategies, then private practice gives you more opportunities to put them into action. You can bring the confusing situations back to your next lesson and ask, “This happened. What should I have done?”
That’s how understanding grows.
Eventually I don’t want a learner relying on me, their mum, their dad, their friend or a sat nav to tell them what to do.
I want them to be able to work it out safely for themselves.
Your sat nav can help you find the road.
Your training should teach you how to read it.
Teach to drive independently not pass a test !
🫶🏼