Filtering on Motorway or Dual Carriageway

Motorcycle filtering in motorway trafficOn my daily commute into London, I invariably find myself having to filter a lot. Some of this is around suburban roads, some on two or three lane A roads, and some in the tightly congested centre of the capital. Today, I’m going look specifically at filtering tips for dual carriageways and motorways.

What is legal?

In the UK, it is perfectly legal to filter through slow moving traffic to make progress. In fact, it is positively encouraged when learning to ride and many a rider will fail their test through ‘failure to make progress’. There are however a few instances where it is illegal to filter:-

No Overtaking
  1. You must not cross an unbroken white line. More specifically, no part of you bike or body should cross or overhang an unbroken white line, except when negating a hazard (stationary vehicle or cyclist, horse, road maintenance vehicle travelling less than 10mph) and it is safe to do so. Slow moving traffic is not a ‘hazard’, I’m afraid.
  2. You must not overtake where there is a no overtaking sign. Obvious really.
  3. You must not overtake the lead vehicle at a pedestrian crossing or within zig-zags. Less well known, but not applicable to motorways.
  4. You must not endanger or cause of other vehicles to change course or speed.

Undertaking vehicles on the near side is not illegal, it is just not recommended, so care must be taken. If you ride like an idiot weaving in and out of lanes, you will be booked for careless driving or possible dangerous driving. It is also perfectly legal to ride on cross hatched areas and central reservation if they are surrounded by a broken white line. However, the Highway Code say you should not unless it is necessary and safe. These areas also build up with debris and loose stones, so be careful.


When filtering, appropriate speed is crucial. Obviously you should never exceed speed limits, but you should keep your speed to within 10-15mph of the traffic you are in. It is also not recommended to filter through traffic travelling faster than 40mph. Ultimately, you should tailor your speed to the gap you’re filtering through. Slow down for tighter gaps.

Traffic jams are full of frustrated drivers who are prone to doing irrational and stupid manoeuvres. Care must be taken and be prepared to stop at seconds notice, which simply isn’t possible at high speed.


Lets run through some general tips for filtering on the motorway, that I’ve picked up on my daily commute:-

  1. If you approach some traffic bunching up ahead, don’t filter immediately. Invariable some drivers will spontaneously change lanes to try and keep moving. Hold back, then filter between two lanes travelling at similar speeds.
  2. Aim to filter between the two outer most (fast) lanes. Nearside lanes tend to be hogged by wider trucks and you can get caught up with those joining or leaving the motorway at junctions.
  3. Anticipate braking at all times, but be wary of covering the brakes lest you reactively grab a fist full in a panic. Keep in a low-ish gear, to make use of engine braking and give you acceleration should you need to zoom out of a closing gap.
  4. Never enter a closing gap, back off and wait. The road may just be narrowing, or there maybe an unseen hazard ahead they’re circumventing, or they may be planning a lane change.
  5. Scan the road ahead, try to spot those about to lane change; look for indicators, front wheels angled, cars positioned far over to one side of lane, or one lane moving faster than another. If you do spot someone about to pull across you, slow down, honk your horn, make your presence known.
  6. Take heed of gaps in the traffic. If a gap reveals itself, expect a car to fill it, possibly cutting across you into it or joining from nearside.
  7. Be mindful of the road surface between lanes. It’s often uneven from joins in the tarmac, will have painted white lines that are slippery in the wet and bumpy cats eye’s. In the winter, it will be less trodden, so may have ice, snow or slush, in which case avoid filtering and just stick to clear tyre tracks.
  8. When following other bikers filtering, try to look beyond them and gauge every gap for yourself. Don’t tail them blindly staring at their back wheel. Gaps change, new hazards can reveal themselves and there’s no guarantee they’re a sensible rider…

I hope some of the above are useful to you. In future posts I’ll cover filtering in the city and suburban roads off the motorway. If you have additional advice and tips, please leave a comment, I’d love to hear from you.

Read the next instalment: Filtering in the City.

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3 replies on “Filtering on Motorway or Dual Carriageway”

Great list!

I have one big tip for beginners: At some point a motorbike may come up behind you who is filtering faster than you. Never be intimidated into matching their speed, merely go back in to a normal lane, let them pass, and then pull out again to filter at your own pace.

Yes, totally agree. Everyone has varying levels of riding confidence (or ideas of safe speeds!), you should never feel pressured to go faster than you’re comfortable with, especially when filtering. London etiquette is to pull over at the next safe gap in traffic and let others by, with those overtaking you often waving or sticking their leg out as a thank you gesture.

When you do pull over to lets others by, and especially on dual carriageways where there can be whole convoys of bikers filtering, do stay mindful of the vehicle in front of you and you check mirrors and look over shoulder to safely pull out and continue filtering again. It’s easy to miss sudden halting of traffic and further bikers coming up from behind.

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