Filtering is moving through traffic that is stopped, either between lanes or to the left or right, while lane splitting is moving through traffic between lanes that are moving slowly or have stopped. Drive in any of the big UK cities and you’ll see motorcyclists and cyclists (usually couriers and commuters) filtering through slow-moving and stationary traffic. On motorways and dual carriageways, you’ll frequently see motorbike riders filtering at higher speeds.
The intent of filtering is to allow motorcyclists to make progress through slow-moving or stationary traffic. It is legal to filter through traffic as long as it is done safely. ‘Safely’ means not causing another driver to alter their course or speed and not when other traffic is fundamentally not queuing. If traffic is moving consistently at 20-30mph or above on a motorway, filtering could bring some unwanted attention by your local constabulary as it could be considered dangerous overtaking.
The Highway Code says “when filtering in slow-moving traffic, take care and keep your speed low.”
The speed differential between you and the other vehicles is important. Motorcyclists are safest when travelling within a speed they can stop at quickly if something goes wrong and not too much faster than the vehicles they are overtaking. Filtering at 20mph through traffic that is crawling at 5mph is acceptable but filtering at 65mph through traffic travelling at 50mph is not. The first example will see you get to your destination four times as quickly while the second example only sees you gain around 30% while massively increasing your crash risk. The slower the traffic you are filtering through, the greater the gain, but the faster the traffic, the greater the risk.
Can you filter when approaching a pedestrian crossing with zigzag lines?
You can filter past all vehicles but must stop behind the first vehicle in the queue, not in front of it (this would usually mean crossing the stop line in front of the crossing anyway). Beware of pedestrians crossing between cars, especially if the crossing is controlled by lights.
If the vehicles have not stopped because of the crossing, but because of congestion, then you are free to pass them without stopping at the crossing, as long as you give way to pedestrians approaching or crossing.
Choosing your filtering point
As traffic begins to come to a stop a motorcyclist who has been scanning will already know that they can filter. The problem is that car drivers don’t tend to scan as far ahead as motorcyclists so will be making last-second decisions about which lane to choose (usually their perception of the fastest lane or the shortest queue). To be safe, a motorcyclist should slow down to join the back of the queue then speed up to start the filtering rather than maintaining a constant pace. Maintaining a constant pace means you risk another vehicle changing lanes in front of you as they won’t be expecting you to be going much faster than the rest of the traffic.
Keep your eye on your mirrors as you have a risk of being run into from a vehicle behind you, but you have the opportunity to dart between the slower cars to evade this.
At the front of a queue you also have more risk because drivers see the traffic speeding up and they will be speeding up, too, as well as looking for opportunities to change lanes now that some differential in speed is established; it’s rare that all lanes speed up at exactly the same pace in the same place.
Watch for apparent gaps in the traffic queue as this could be a space someone is leaving to let another driver out of a side street or driveway.
Filtering at roundabouts is not ideal because traffic is trying to judge the correct gap to emerge; they are not thinking about a motorcyclist arriving from behind. While there’s the temptation to gain a few car lengths, the risk is amplified. Don’t trust the signals that vehicles are giving on roundabouts, either, as many people don’t know how to signal properly.
When filtering at traffic lights beware of pedestrians walking between cars. Try to avoid filtering if you don’t think you will make it to the red light before the lights go green; the worst situation is when you arrive at the head of the queue just after the lights go green and the lead car hasn’t seen you. It’s OK to stop a couple of cars back and ensure that the driver just behind you has seen you. Don’t start filtering as vehicles are pulling away from the lights as they are focusing on what the vehicle in front of them is doing.
It’s generally best to filter between the outside lane (furthest to the right) and the one next to it as you will avoid the majority of trucks.
Only overtake vehicles to the left if they are turning right or you are turning left in a dedicated lane. The outside is a better position but you must be aware of drivers turning right, traffic coming from ahead and obstructions such as traffic islands. Generally, it’s safer to overtake if you move to the opposite carriageway when it’s safe to do so.
Solid white lines
If you can pass the vehicle without crossing the solid white line, this is perfectly legal. Bear in mind that the solid white line is there for a reason (e.g. limited visibility of a hazard), so you need to choose whether it’s actually an appropriate place to overtake.
If you are too close to the vehicle you are overtaking, police may prosecute for careless driving. Note that there is no specific guideline for ‘too close.’
You can use bus lanes unless they in use as bus-only lanes. Technically this is not filtering because you’re already allowed to use the lane. Watch for people turning across the bus lane to enter driveways.
Smaller towns and villages
In cities drivers tend to be used to motorcyclists filtering but if you try to do this in a village in the Scottish Highlands, where drivers aren’t looking out for you, you increase your accident risk dramatically. Conversely, if you haven’t driven in London or Manchester, be prepared to be thrown in at the deep end. Take it easy to start with until you get used to the traffic flow.
Why is filtering good?
Filtering improves traffic flows. Filtering allows the cars and lorries in a traffic queue to bunch up together rather than being separated by the faster motorbikes. The motorbikes leave quickly at the front of the queue meaning more of the other vehicles can get through a particular phase in the traffic lights.
Filtering saves fuel. Motorcyclists don’t end up burning fuel unnecessarily.
Filtering moves motorcyclists to a safer position at traffic lights. The motorcyclists start at the green light at the head of the queue rather than being surrounded by other vehicles where they are more likely to be in other motorists’ blind spots.
Why is filtering bad?
Driver frustration. Other drivers can feel a sense of frustration that other road users are jumping the queue, leading them to make rash decisions.
Accident risk. There are mixed opinions: some say that motorcyclists that remain in the traffic flow are more likely to be hit than if they are filtering while some say that motorcyclists tend to be involved in crashes (albeit generally minor ones) when they are filtering. For inexperienced motorcyclists, smaller gaps between large vehicles presents more of a challenge. It seems motorcyclists can’t win either way.
Risk of damage. Occasional damage by motorbike riders squeezing through gaps that are too tight.
Blind spots. Filtering closely down the side of a large lorry or just in front of it often puts a motorcyclist in the lorry’s blind spot.
Motorway speed filtering is dangerous. Filtering above 30mph increases the risk of an accident because other motorists aren’t expecting this kind of manoeuvre to happen.
Things to avoid when filtering
On a motorbike, don’t filter between the kerb and a line of cars as they won’t expect you to be there and there’s not usually enough room. Cyclists do this all the time, but generally at a lower speed. Sometimes people will exit from the passenger seat at lights.
Don’t use cycle lanes or the footpath (it’s illegal). If you are filtering where a cycle lane has been installed, beware of narrower lanes. Often, the space required for the cycle lane is cribbed from the vehicle lanes, leaving you less room for filtering.
Don’t be a bad ambassador for filtering. You already have a small segment of car drivers against you, so don’t make this worse. Knocking a car’s wing mirror is an absolute no-no.
Don’t ride aggressively. If you have an accident you don’t want 30 drivers you’ve just overtaken all standing as witnesses against you.
Don’t filter as you approach a side road because you will be hidden in other vehicles’ blind spots but will be travelling faster therefore you risk someone pulling across in front of you.
Don’t keep changing lanes to gain an advantage; this will be frowned upon by the police and you are likely to be stopped and ticketed.
Don’t use your hazard warning lights when filtering.
Etiquette when filtering
Always acknowledge car drivers that change lane position to help you pass through the traffic.
Let faster riders past rather than increasing your speed if you don’t feel safe.
Know the filtering rules. Many drivers don’t and they will challenge you. You have an opportunity to remind them that filtering reduces traffic jams and pollution (better for them).