Slow moving queue of traffic: rules 151 and 163
Updated •4 min read
You're driving in a slow moving queue of traffic: stay in your lane and do not change lanes to the left to overtake. That is Highway Code rule 163 ("stay in your lane if traffic is moving slowly in queues") and rule 151 ("not change lanes to the left to overtake").
Rules on this page are quoted from the Highway Code on gov.uk: rule 163 and rule 151, read on 27 October 2026.
What rule 151 says about slow-moving traffic
Rule 151 says you should:
- reduce the distance between you and the vehicle ahead to maintain traffic flow
- never get so close to the vehicle in front that you cannot stop safely
- leave enough space to be able to manoeuvre if the vehicle in front breaks down or an emergency vehicle needs to get past
- not change lanes to the left to overtake
- allow access into and from side roads, as blocking these will add to congestion
- allow pedestrians and cyclists to cross in front of you
- be aware of cyclists and motorcyclists who may be passing on either side.
What rule 163 adds
Rule 163 says to stay in your lane if traffic is moving slowly in queues. It adds: "If the queue on your right is moving more slowly than you are, you may pass on the left." So passing on the left is allowed only when the queue on your right is slower than you are, not when you move over to the left to get ahead.
Why the tempting alternatives are wrong
| Option | Why it fails |
|---|---|
| Move to the left lane to get ahead | Rule 151: do not change lanes to the left to overtake |
| Drive close behind the vehicle in front to stop others cutting in | Rule 151: never get so close that you cannot stop safely |
| Block the side road so nobody else can get out | Rule 151: allow access into and from side roads |
| Stay in your lane and keep a safe gap | Right: rules 151 and 163 |
Cyclists and motorcyclists
Rule 151 warns that cyclists and motorcyclists may be passing on either side. Check your mirrors and blind spot before you move, even in a crawl. Our overtaking guide covers when you must not overtake and how much room to give a cyclist.
A worked example
You are in the right-hand lane of a two-lane road in a long queue, and the left lane starts to move a little faster. The tempting move is to switch into it to get ahead. Rule 151 says not to change lanes to the left to overtake, and rule 163 says to stay in your lane when traffic is moving slowly in queues. Keep your gap, keep your place and let the queue clear.
Test yourself
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Frequently asked questions
You're driving in a slow moving queue of traffic. What should you do?
Stay in your lane and do not change lanes to the left to overtake (rules 151 and 163).
Can you overtake on the left in a slow-moving queue?
Only if the queue on your right is moving more slowly than you are (rule 163). Do not change lanes to the left to do it.
Should you leave a gap at side roads in a queue?
Yes. Rule 151 says to allow access into and from side roads, as blocking these will add to congestion.