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The Highway Code – What Does it Say About Undertaking?

Have you ever seen a driver speed down on the inside of another car on the motorway, frustrated because the driver in the middle lane is ‘going too slow!’, or ‘won’t get over’? This is called undertaking.


What is undertaking?


It is the practice of overtaking a slower moving vehicle on it’s left-hand side (kerb side).


Unfortunately, this is a much more common sight on UK motorways than we’d hope for.

Can I do it?


Although not strictly illegal, undertaking is strongly discouraged by The Highway Code, stating “do not overtake on the left or move to a lane on your left to overtake.” However, there are exceptions that apply when a car undertakes in slow-moving traffic if its lane is moving faster than a lane on the right, undertaking in this circumstance is often deemed safer than weaving in and out of traffic.


Rule 268 of The Highway Code states: “In congested conditions, where adjacent lanes of traffic are moving at similar speeds, traffic in left-hand lanes may sometimes be moving faster than traffic to the right. In these conditions you may keep up with the traffic in your lane even if this means passing traffic in the lane to you right. Do not weave in and out of lanes to overtake.”


Other conditions where undertaking may be appropriate:

  • Average speed checks
  • If a vehicle in front is turning right or U-turning (although it is often safer to wait until the vehicle has completed the turn)


Remember; Rule 267 of The Highway Code states: “Only overtake on the right”

Overtake a car caravan trailer on swiss autobahn highway

Is it dangerous?


Undertaking is not to be underestimated. It can cause serious accidents, especially at high speeds on motorways. As it is not standard practice, it can take other road users by surprise and can therefore cause sudden swerving and distraction.


Could I get in trouble?


If you undertake inappropriately, you could receive a fixed penalty notice (FPN) for careless driving or driving without due care and attention. This could possibly result in 3 points on your license and a £100 fine if it is a minor offence, further sanctions could be imposed depending on the extent of the offence.

tailgating on a three-lane autobahn

Advice from RED


If you find yourself needing to undertake, for example in slow moving traffic where you’re moving at similar speeds, be aware that the driver ahead may not be checking their inside mirror and/or blind spots before pulling in, so proceed slowly and with caution.

Like with many situations when driving, you’ll need to lean on your previous experience to judge whether it’s safe to conduct this manoeuvre.

If you’re caught weaving in and out of lanes and driving erratically then you could end up with an FPN on your hands!

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Here at RED Driving School we want to ensure you pass your driving test with minimum fuss and hassle. With Independent Driving introduced to the practical driving test today, it’s important you still remember the fundamental things you should and shouldn’t be doing on your driving lessons and driving test!



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