When you overtake a slow-moving vehicle on its left-hand side (also known as the kerb side), it is called “undertaking”. But is undertaking illegal in the UK? It can be a dangerous manoeuvre and can be punished as careless driving if you are not extremely careful.
In this guide, we will explore exactly what undertaking is in driving, when is it okay to undertake a vehicle, and the penalties involved if it is deemed dangerous driving. We will also highlight safe driving practices for drivers so they can identify situations where undertaking is illegal, what to do if you are caught, and how this can be different for personal and professional drivers.
There are many different laws centred around driving, and there are some that may not come immediately to mind. We have another guide on is it illegal to drive barefoot if you would like some more insights into often forgotten driving laws.
What is undertaking and why does it matter?
Undertaking is the practice of overtaking a slower moving vehicle on its left-hand side. This is commonly seen on UK motorways, but is it illegal, and can you get fined for it?
There is no undertaking law in the UK, but the Highway Code strongly discourages it. This is because it can be highly dangerous, especially on roads where traffic is moving at high speeds. As it is not a standard practice, it can take other drivers by surprise, leading to sudden swerving and distraction.
If undertaking is carried out in a way that is considered careless or dangerous, you can be prosecuted for careless driving.
Understanding undertaking on UK roads
Despite the Highway Code discouraging undertaking, there are situations where it may be acceptable.
For example, undertaking may occur on a dual carriageway in slow-moving traffic, if its lane is moving faster than a lane on the right. In these cases, it is considered safer to undertake than to weave in and out of cars, which could lead to even more accidents.
Undertaking may also occur in congested conditions (especially on motorways), where adjacent lanes of traffic are moving at similar speeds. This often leads to the traffic in the left-hand lane moving faster than the traffic to the right, which means drivers can keep up with traffic in their lane, even if it means passing traffic to your right.
Legal vs illegal undertaking
In most cases, it is better to assume that undertaking is unacceptable, and it should be avoided to drive as safely as possible. On the other hand, there are certain cases where it won’t lead to a penalty or fine.
These situations include:
- You can undertake on motorways where average speed limits are in operation.
- If there is a car that is turning right or U-turning.
- On these motorway sections, overhead gantries often instruct drivers to “stay in lane.” As a result, if your lane is moving faster, it may be safer to pass a slower vehicle on the left rather than changing lanes. This approach is still preferable to repeatedly weaving through traffic.
General best practice
On a motorway, you should normally overtake on the right and should not move into a lane on your left simply to pass another vehicle. However, in congested conditions, where adjacent lanes are moving at similar speeds, you may stay in your lane and keep up with the traffic even if this means passing vehicles in a lane to your right. This can occur when there are roadworks or sections with reduced speed limits, but the presence of an average speed limit does not itself make undertaking permissible. Drivers should also avoid weaving between lanes to overtake.
Risks of undertaking
If the authorities determine your undertaking was unsafe, you can be penalised for it. Read on to find out the illegal implications of undertaking and what this can mean for your insurance, licence points, and personal fines.
Fines, penalty points, and insurance implications
The temptation to undertake may be strong, especially if you’re dealing with a middle-lane straggler, but in doing so you could wind up with a hefty fine.
Undertaking when you don’t have any cause to doing so could see you receive a fixed penalty notice (FPN) for careless driving or driving without due care and attention. This often leads to a £100 fine and three points on your licence, but you may be offered a driver education course as an alternative.
When the case is considered dangerous driving, meaning it could have caused harm to yourself or others, harsher penalties may be doled out. This can lead to up to nine points on your licence or even disqualification, or a fine of up to £5,000 and a court summons.
Any of these fines or penalties can ultimately lead to your insurance being negatively impacted. Having points on your licence indicates to insurers that you are a higher risk, which can cause your insurance premiums to increase significantly when your policy renews. Also, if an accident occurs because you carried out an inappropriate undertaking, the insurer may determine your actions were reckless or dangerous and your claim can be rejected or your policy voided altogether.
Even if undertaking was permitted in slow traffic, insurers could still investigate factors such as:
- Driver positioning
- Speed differences
- Dashcam footage
- Highway Code compliance
Differences for personal or business drivers
As there is no strict law regarding undertaking, there is not much difference between the consequences for professional and business drivers. There are more glaring dangers when driving professionally, however, due to professional accountability and the vehicles that business drivers tend to use:
- Business drivers (such as vans, delivery trucks, or taxi drivers) often drive commercial vehicles equipped with safety accessories like dashcams and black boxes, so there will be more proof and accountability of any dangerous undertaking. If this is caught, it could lead to dismissal or a severe impact on fleet insurance premiums. Business drivers may also face employment, licensing, or regulatory consequences, but these are additional and don’t happen automatically.
- The prosecution of careless driving also differs. Whereas personal drivers may only receive three points on their licence and a £100 fine, business drivers risk being reported to the Traffic Commissioner. This can then end in them losing their vocational driving entitlement, effectively ending their career.
- Business drivers are also usually driving higher-risk vehicles, such as delivery vans and HGVs, which have massively restricted left-hand visibility. Larger vehicles cannot often see a vehicle passing down their inside, so undertaking in this situation creates a high-collision risk, which needs to be avoided as much as possible.
If you are someone who drives a van professionally, you may want to check out our guide on van speed limits.
Safe driving alternatives
Sometimes, undertaking may be unavoidable and can be safer than weaving through motorway or dual carriageway traffic. If it must be done, there are certain scenarios where undertaking is acceptable, and if you understand these you can minimise risk while doing so. There are also some safe driving alternatives we will discuss in this section that may be a better decision over undertaking.
When undertaking is allowed
We have listed below the only times undertaking may be considered acceptable. Take a look:
- Slow-moving or congested traffic – if traffic is heavily congested and the left lane is moving faster than the lane on the right, drivers are permitted to continue progressing in their lane. Staying in a lane and gradually passing traffic on the right is considered acceptable in this scenario because changing lanes repeatedly would create more risk.
- Average speed check areas – roads with average speed cameras usually display “stay in lane” signs. In these situations, traffic flows are more controlled, and drivers may legally continue in their lane if it moves faster than traffic on the right.
- When a vehicle turns right – it may be safe to pass a vehicle on the left if the driver is positioned to turn right or perform a U-turn. This should still be treated with care and squeezing through small gaps should be avoided.
Safer overtaking practices
Choosing to overtake on the right is a much better decision than undertaking, as it aligns with driver expectations, vehicle design, and traffic laws.
The reasons why overtaking is considered safer than undertaking are:
- Blind spots – drivers have better visibility on their right side. Undertaking means you are being placed in a large blind spot.
- Driver expectations – most drivers do not expect to be passed on the left. This unpredictable move can lead to collisions and other accidents.
- Defensive space – passing a vehicle on the right gives you more time to react if the car moves suddenly.
To make sure you overtake safely, there are a few steps you should take. These include:
- Check the signs and scan ahead – you need to make sure road markings allow passing and that there are no hazards or restrictions ahead. You can then drop back to maintain a safe following distance, as this will also improve your view.
- Check your mirrors and signal – check for vehicles behind you before you start overtaking. Once that is done, you can signal and inform others of your intent.
- Overtake safely – execute the manoeuvre by matching the speed needed to pass quickly. Never get close to the vehicle ahead before pulling out, and make sure you can see the passed car in your central rearview mirror.
- Return to the lane – signal you are about to move back into the lane and maintain a safe, legal speed. Do not cut off the vehicle you passed when you return.
What to do if you are caught undertaking
So, what should you do if you are caught undertaking? Depending on the situation and the severity of it, there may be different penalties given out, and each would need to be dealt with accordingly.
Understanding your penalty
There will be different penalties for undertaking depending on the scenario, and what the authorities deem it.
If the manoeuvre was deemed as careless driving, the penalties will include:
- Fixed penalty notice - £100 fine and 3 points on your licence.
- Penalty points – 3 to 9 penalty points (depending on the severity of the case).
- Driver awareness course – offered in some cases for minor first-time infractions.
- Insurance impact – higher premiums due to less insurer confidence.
In serious cases, penalties can become much more severe if the authorities deem your undertaking as dangerous driving. The penalties for dangerous driving are:
- Unlimited fines
- Mandatory driving bans (typically 12 to 36 months)
- Substantial increases in insurance costs
- Court prosecution and potential imprisonment
When deciding on penalties, the police and courts will consider:
- Traffic conditions
- Speed
- Driver behaviour
- Risk created for other road users
A lot of these penalties are serious sanctions and should be avoided at all costs. This is why avoiding careless undertaking can be just as important as knowing how to drive safely in strong wind.
Steps to avoid repeating offences
To make sure you never repeat the same undertaking offences, there are a few steps you can take:
- Become a master of lane discipline – as a rule, you will want to stick to the left-hand lane unless you are actively overtaking another vehicle. Don’t be tempted to weave in and out of cars just to make faster progress.
- Understand the congestion exception – you are technically allowed to undertake vehicles in heavy, slow-moving traffic. However, if you are moving to the left lane just to bypass a slower vehicle, this is considered careless driving.
- Perform smart observations – make sure to always check your centre and right mirrors before undertaking and always signal early. You will need to check your right-hand blind spot before moving out as well.
- Don’t act on impulsive reactions – it’s tempting to undertake “middle-lane hoggers”, but don’t let that frustration take over. A reckless undertake and weave can be seen as careless or dangerous driving, and penalties and fines can be issued.
If you stick to these steps, you can avoid dangerous undertaking and avoid fines and insurance rises.
Leasing made easy with Leasing Options
Now you know the laws and technicalities around undertaking, it’s time to get out on the roads. If you’re looking for affordable, easy, and honest lease deals, then choosing to lease a vehicle with Leasing Options is your best bet. Our staff are always eager to help you find the best deal possible, so if you have questions, don’t hesitate to contact our team. You can also view our best car leasing deals where we have an extensive selection of deals on offer.
Finally, if you need some more advice before signing your new deal, check out our helpful car leasing guide.
