You’re cruising along at a steady pace when the traffic in the right lane suddenly slows down, leaving you wondering if undertaking is illegal. While some common driving advice suggests it’s always off-limits, the reality is a bit more nuanced. In this article, we’ll break down the rules and what you need to know about undertaking in the UK.
Let’s start by clearly defining the term to ensure we’re on the same page, then cover the actual rules. The key takeaway? Undertaking isn’t always illegal or wrong — it’s more about using good judgement than strictly avoiding it.
What is the difference between overtaking and undertaking?
Overtaking another car is when you pass on the offside, while undertaking is passing on the nearside. In cars built for the country they are in, that’s the driver’s side and passenger’s side respectively.
In the UK we drive on the left, so overtaking is passing on the right and undertaking is passing on the left. It’s not just on single-lane roads where you overtake as passing another car on a multi-lane road like a motorway is also overtaking or undertaking. You can also call undertaking something similar, like ‘passing on the left’ or ‘overtaking on the left’.
Is it illegal to undertake?
The Highway Code is the best place to start for driving-related questions including about undertaking. The rule here is pretty clear: ‘do not overtake on the left or move to a lane on your left to overtake.’ However, there’s more when you read on.
Highway Code rule 268 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 lanes to your right. Do not weave in and out of lanes to overtake.’
So the rules say not to undertake, but also that you can in some situations.
When is it acceptable to undertake?
Let’s look at an example to consider when it is and isn’t acceptable to undertake.
On a three-lane motorway with heavy traffic, if lane one is moving slightly faster than lanes two or three, it’s generally okay for vehicles in lane one to undertake the slower traffic, as long as they don’t switch lanes to do so. However, moving from lane three to lane one just to pass cars isn’t advisable unless you do so gradually with plenty of space.
Undertaking is also acceptable in a traffic jam, where all lanes are moving slowly. Just keep a safe distance and stay in your lane.
When is it not acceptable to undertake?
There are more circumstances in which undertaking isn’t acceptable than circumstances in which it is. Here are just a few examples. It’s not acceptable to cut through small gaps in traffic to get to another lane that’s travelling faster. If the first car ahead of you has left a large gap to the second car, it’s not acceptable to pass the first car on its left-hand side to get into the gap.
If there’s a car in lane two travelling at 50mph and you’re in lane one travelling at 70mph, it’s not acceptable to undertake that car at undiminished speed. Overtake it on the right-hand side or, if that’s not possible, slow down to a speed at which you’ll gradually move past the car.
What constitutes unacceptable undertaking is, to a large extent, in the eye of the beholder. But here’s a rule of thumb: if an undertake causes another car to brake or swerve, or the driver is startled by the move, it’s not acceptable. Indeed, it becomes a punishable offence.
Can you get points for undertaking?
Undertaking in an unacceptable manner is considered careless driving or driving without due care and attention. You could get caught by a police patrol or enforcement camera or be reported by a member of the public with dashcam footage. The minimum penalty for an unacceptable undertake is three points on your driving licence and a £100 fine.
However, particularly egregious incidents of undertaking can constitute dangerous driving. The punishment in such cases can be a fine of several thousand pounds and a multi-year driving ban.
Is it an offence to overtake?
Overtaking is perfectly legal, however doing so under certain circumstances can be an offence. It’s illegal to cross a solid white line or an area of hatch markings in the centre of the road; an overtake that causes oncoming traffic to brake heavily or swerve out of the way would also be an offence.
Overtake under the wrong circumstances and you could be charged with careless driving, driving without due care and attention, or even dangerous driving. The penalty can range from a £100 fine and three points to a driving ban of several years. An example of that could be a driver overtaking without checking for other traffic and causing an accident.
Can you undertake on a slip road?
The rules and guidelines discussed earlier in this article apply on any multi-lane road. So, if there is a slow-moving vehicle in the right-hand lane of a multi-lane slip road, it would be acceptable to undertake, so long as you don’t go past at much higher speed. Remember, the point of a slip road is to get up to the same speed as the traffic on the main carriageway and you may have to undertake another vehicle to do so.
Can you undertake on a roundabout?
Passing a slow-moving vehicle on the left-hand side on a multi-lane roundabout can be acceptable, so long as you abide by the rules and guidelines discussed earlier in this article. However, you should exercise a high degree of caution, in case the vehicle on your right makes a late attempt to cross multiple lanes towards an exit.
Is undertaking more common in certain types of traffic?
Yes, undertaking happens more often in heavy, slow-moving traffic when lanes are crawling at different speeds. Still, it’s best to play it safe and stick to passing on the right whenever you can.
