When You Can Overtake a Vehicle from the Left

In the UK, driving rules are meticulously designed to maintain order and road safety. One aspect of these rules is overtaking, which traditionally occurs on the right side of a slower-moving vehicle. However, there are circumstances where overtaking on the left, commonly referred to as undertaking, is permissible. Understanding these rules can help drivers navigate the roads more safely and efficiently.

The General Rule of Overtaking

In the United Kingdom, the Highway Code, which provides guidelines and rules for road users, specifies that overtaking should generally be done on the right. Rule 163 states that drivers should overtake only when it is safe and legal to do so, and they must ensure they have a clear view of the road ahead and that there is no oncoming traffic.

Overtaking on the left is typically discouraged as it can lead to confusion and accidents, given that most drivers expect to be overtaken from the right. However, there are specific scenarios where undertaking is permitted, and understanding these exceptions is crucial for safe driving.

When Undertaking is Allowed

  1. In Congested Traffic: When traffic is moving slowly in queues, and the lane to the right is moving more slowly than the lane you are in, the undertaking is allowed. This often happens in heavy traffic conditions where vehicles are moving at a crawl. According to Rule 268 of the Highway Code, drivers can pass slower-moving traffic on their right if their lane is moving faster. During peak traffic hours, this manoeuvre is typically seen on motorways and dual carriageways.
  2. When Directed by Signs or Road Markings: Road signs or lane markings may sometimes direct traffic to undertake. For instance, on some multi-lane roads, there may be signs indicating that a particular lane must turn left or go straight while the right lane is designated for right turns only. In such cases, if you are in a lane that allows you to go straight or turn left, and you find yourself passing slower traffic on the right, it is permitted.
  3. In Filter Lanes: Filter lanes, or lanes that branch off from the main road to allow for turning left, can also present situations where undertaking is allowed. If you are in a filter lane and the traffic in the main lanes is slower, you may pass these vehicles on their left.
  4. One-Way Streets: On one-way streets, the undertaking can be permissible since the flow of traffic is often more flexible. All lanes on a one-way street may be moving in the same direction, so overtaking on either side might be acceptable depending on the circumstances.
  5. When a Car in Front is Turning Right: If a car in front of you is indicating and positioned to turn right, and there is enough space to safely pass on the left, undertaking is allowed. This is particularly common in urban areas where right turns can often cause temporary obstructions in the right-hand lane. According to Rule 163 of the Highway Code, when a vehicle ahead is waiting to turn right, drivers are allowed to pass on the left if it is safe to do so.

Risks and Considerations of Undertaking

While the undertaking is legal in certain situations, it carries inherent risks and should be approached with caution. The primary danger lies in the fact that drivers do not typically expect to be overtaken from the left, which can lead to sudden lane changes or swerving if they do not notice an undertaking vehicle.

Here are some key considerations to keep in mind when undertaking:

  • Stay Alert: Constantly monitor the actions of the surrounding vehicles. Be especially mindful of indicators and brake lights, which can give you clues about other drivers’ intentions.
  • Maintain Safe Speeds: Avoid excessive speed while undertaking. The goal is to pass safely, not to race past the slower traffic.
  • Signal Your Intentions: Use your indicators if you plan to switch lanes after undertaking, ensuring that other drivers are aware of your movements.
  • Check Blind Spots: Always check your blind spots before making any manoeuvres. Other vehicles, particularly motorcycles or cyclists, might be less visible and could be in your blind spot.
  • Anticipate Hazards: Look out for pedestrians, especially in urban areas, where they may be crossing the road between slow-moving or stationary vehicles.

Legal Implications

The undertaking, when not performed under the permissible conditions, can be considered careless or even dangerous driving. The penalties for such offences can be severe, ranging from fines to points on your driving licence, or even disqualification in extreme cases. It’s important to be aware of and adhere to the rules set out in the Highway Code to avoid legal repercussions and to ensure the safety of all road users.


Undertaking is a manoeuvre that, while generally discouraged, is permissible under specific circumstances in the UK. Understanding when and how to safely undertake is crucial for responsible driving. By following the guidelines provided by the Highway Code and exercising caution, drivers can navigate the complexities of road traffic more effectively and safely. Always remember that the primary goal is to maintain safety and order on the roads, and sometimes, that means knowing when not to undertake, even if it is legally permissible.

Posted on Jul 3, 2024 by Sam

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When You Can Overtake a Vehicle from the Left


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