Filtering - what's legal and how to do it
If you've looked at the Bike Magazine video that appeared in June
00, you'd have seen some filtering going on. If you ride in London
you'll see couriers filtering all the time, through slow moving and
stationary traffic. Out on the motorways, you'll often see riders
filtering at speed.
So is it legal and is it safe?
Let's deal with the legal aspect first. There is a very fine line
between filtering and lane splitting or undertaking. The latter is
an offence which could see you in court and walking away with
points, a ban or even a custodial sentence if it was considered to
be dangerous enough.
Whilst there are no clear definitions of what is acceptable and what
is not, there are several sections in the Highway Code which refer
to overtaking. Let's mention the places you must not overtake first.
You may not:
cross solid white lines except to pass an
obstruction or to overtake a slow (10mph), horse, bicycle, local
authority vehicle (with its amber beacon flashing)
overtake after passing a No Overtaking sign,
until you reach the end of restriction sign
overtake the vehicle nearest a pedestrian
crossing (most foot plod think you cannot overtake on a crossing
inside the zigzags - this is what the Highway Code says - so it is
probably safer to apply the broader rule)
However, you may overtake vehicles where there is a solid white line
on your side of the road if you can pass the vehicle without
crossing or straddling the white line with any part of your vehicle.
enter a hatched lane divide as long as it has
dashed boundary lines and it is safe and necessary to do so
pass traffic on the left (ie undertake) queuing
or slow moving traffic but you should not change lane in order to
gain an advantage
pass traffic on the left if the vehicle is
indicating to turn right
pass traffic on the left if you are turning left
in a dedicated left turn lane
pass traffic on the left in a one way street
So we still haven't actually said anything about filtering.
Motorcycle Roadcraft explains that filtering is a form of overtaking
to make progress past stationary or slow moving traffic but gives no
real advice on where or where not to do it. You might be surprised
to know that filtering is taught on basic training courses in
congested areas and the DSA examiner will expect to see it applied
on test if appropriate. Needless to say, as an ex-courier in London,
I used to do it all the time.
So what rules do we use for basic training? The prime rule is
safety, both for the rider and for other road users who may not be
expecting a motorcycle to appear from between queues. Watch out for
pedestrians crossing the road or leaping from taxis or buses, and
motorcyclists and cyclists weaving through the traffic.
When passing stationary traffic on a single carriageway road, it is
generally safer to move into the opposite carriageway if possible,
and to move back when confronted by oncoming traffic or when further
progress cannot be safely made. Filtering may take place against
oncoming traffic provided there is a sufficient safety margin - if
necessary slow down. Don't forget that you should never force
another vehicle to swerve or slow down - if you are seen to do so,
this could count as grounds for a prosecution. Watch out for
junctions, where cars can turn across you, or turn right from beside
you - only filter past them when you have a good view.
Don't forget it is perfectly legal to use bus lanes when they are
not in use - check the sign boards at the beginning of the lane -
but do so care as someone else may suddenly get the same idea. Avoid
filtering up the left of traffic next to the kerb- drivers are
simply not looking for you, and are even more likely to turn left
Passing between traffic queuing in lanes is usually relatively safe
but expect vehicles to change lane from either side of you, and
watch out for motorcycles and cycles weaving in and out.
On a dual carriageway with three lanes, between lane 2 and lane 3 is
usually the best bet. Lorries are not allowed to use the outside
lane so you have more space and a better view. In addition you are
less likely to be sideswiped by vehicles changing lanes at or near
junctions. On the other hand you have more danger from impatient car
drivers swapping lanes without warning. Be very careful when one
lane stops altogether and adjust your speed to that lane - someone
WILL try to swing into a gap in the moving lane!
Keep your speed down whilst filtering - in slow moving traffic my
rule of thumb is never to go faster than a speed that allows me to
stop if the car in front suddenly opens its door or pulls a U turn.
This is generally no more than around 10-15mph faster than the
traffic I am passing. If traffic starts to move much over over 50%
of the speed limit (eg. at around 40mph on a national limit dual
carriageway), I usually return to the lane.
Be ready to use the horn, and use your headlight - consider using
main beam - it's technically illegal but gives you a much better
chance of being seen. Plan ahead - look for obstructions like
traffic islands, bollards, side roads where vehicles might emerge or
turn across your path, look for spaces to move back into the queue,
and look to make eye contact with drivers if you need to move back
into a gap. Watch traffic light sequences so that you can plan
whether you can slip to the front whilst they are red or need to
look for a gap in the queue into which to move when the lights
change. Watch for potholes, painted lines or slippery surfaces that
could make braking or steering difficult. Watch for width
restrictions, cars waiting to turn right or cycles that might
squeeze lanes together. Be careful passing lorries and buses - not
only do they need space to turn at junctions or on sharp corners and
may cut across your path, don't forget your view past them is also
very restricted and they cannot see you if you cannot see the driver
in his mirrors. Treat an apparent gap in the traffic with caution,
particularly if the queue in front of the stationary vehicle is
moving - you can almost guarantee the driver is letting someone out
from a side road or to turn into the side road from the opposite
Don't forget, you may not pass to the right of a keep left sign or
enter a cycle lane (if bounded by a solid line), bus lane (check the
times it is active) or tram lane. Nor should you cross the solid
white stop line at traffic lights - in practice doing so gives you
the edge on making a clean getaway. Passing in cross hatching with a
broken boundary is allowable if "safe and necessary". Unfortunately
your idea of necessary may not be the same as the policeman's!
Be careful about moving back and forth to the fastest moving lane on
a multilane road to make progress in heavy traffic. A traffic
policeman friend on a training course was shown a video of a
motorcyclist moving at speed from lane to lane on a busy motorway
and asked for comments. He suggested that he was riding safely even
if not strictly within the letter of the law and that he had no
problem with what he saw - he was surprised to be told that the
rider had been prosecuted successfully for dangerous driving and
banned! I regularly see riders weaving in and out of traffic at 80
or 90mph on the M25 - aside from the likelihood of getting a pull,
the chances of avoiding a car suddenly changing lane are virtually
zero! Using the hard shoulder to pass stationary traffic on a
motorway is illegal.
Be careful about using a lane which has a "turn left" or "turn
right" arrow in it to make progress past stationary or slow moving
traffic. Although it is not technically illegal to return the
straight ahead lane at the end of it, many police will take a dim
view. Likewise, exercise caution when making a turn from a lane
marked with a straight ahead arrow.
What do you do when baulked by a lane hog? Well, the bad news is
passing on the left is can constitute 'dangerous' or 'reckless'
driving in the opinion of the policeman. This can get anything from
3-6 points on the licence to a custodial sentence! Don't sit a metre
off his back bumper with main beam on either. Generally a position
to the offside of the car will make you visible in the rear view and
driver's door mirror and given time and perhaps a flash of main
beam, they will generally spot you and move over. Don't just blast
by - give a them a "thank you" wave.... it makes it more likely they
will do the same for another rider in the future.
Be courteous to other road users. Don't harass or hassle them - most
or doing their best (even if it may not be very good) and many
drivers do not like driving in traffic and are nervous enough
without having a bike apparently trying to join them in the driver's
seat. An impatient, aggressive motorcyclist can easily distract them
or cause them to make a mistake. Don't forget that a highly
manoeuvrable bike weaving through stationary traffic is also high on
the hate list of aggressive car drivers - you will meet the odd one
who will try to take you out!!
Go with local practice - trying the same filtering techniques that
you use on the Euston Road in London in a small Scottish village is
asking for trouble, because noone will be on the lookout for you.
In general you can assume that a traffic policeman will know both
the letter of the Highway Code and motoring law and the spirit of it
too, will quite possibly be a biker himself, and will give you
credit for riding sensibly, but ride like a prat and you'll get your
wrists slapped. Panda car drivers will often only have a sketchy
knowledge of what's legal and what isn't, whilst a foot plod will
usually know almost nothing - to them almost everything you do on a
bike looks dangerous, and don't forget in court it's usually your
word against the policeman's! If you get that far, unless you have a
very good (read expensive) brief, it's game over - the magistrate
will believe the copper's every word.
Finally, if you are not confident you can do it, don't! You might be
capable of dealing with your home town's traffic problems but London
in particular is another kettle of fish! It might take you a little
longer to reach your destination, but it's better to arrive on the
bike than in the air ambulance.
In conclusion, the best traffic filterers take no chances, but make
good progress by combining excellent observation with careful
planning. Looking as far ahead as possible will allow you to spot
potential bottlenecks and allow you to get into the best position to
deal with them. The best despatch riders move through traffic almost
imperceptibly - but they are always there at the head of the queue.