Theres much debate about the merits and legality of filtering through traffic. When does it become lane splitting? What are the rules on getting through traffic? If truth be told, there are some grey areas. To a large extent we are reliant on the discretion of traffic officers. In the vast majority of cases, you will have no problem if you are filtering through traffic sensibly and with due care for your and others safety.
In the cut and thrust of urban riding, the simple fact is you will want to move though queues of vehicles, get to the front at traffic lights and generally make progress through traffic. Otherwise there wouldnt be much point in riding a motorbike and youd just contribute to congestion.
Advanced riders, including police riders, understand that getting boxed in by other vehicles is less safe than proceeding through traffic. But either way, riding in such close proximity to other vehicles has risks.
Imagine two lanes of traffic are stopped for the lights. You want to get to the front and make a quick getaway using the bikes acceleration, so youre looking at the gap up the middle or using the opposite carriageway to overtake. Problem: what if the lights change to green before you complete the manoeuvre? You could be on the wrong side of the road with oncoming traffic. Or someone in your carriageway decides to turn right. Or you could be stuck between two lanes of vehicles moving off from the lights.
You have to make sure you have time to get to the front at a safe speed. You dont really want to be passing within centimetres of stationary vehicles at more than about 20 km/h. That means knowing the light phasing and when they are going to change. Easy on your regular route home but harder in a new part of town. So hang back and learn. Dont be tempted to barrel into danger.
And even when you know the light phasing, someone still might open a car door. Move slowly and look for any sign of danger.
Moving through the middle of moving traffic is where the local cops will take a dim view. And with good reason. Stationary cars cant chop lanes suddenly, moving vehicles can. Overtaking, using a clear opposite carriageway, is one option, but youre still going to need somewhere to pull back in.
Moving up the middle puts you in danger of a vehicle changing lanes just as you come alongside.
If the queues are moving very slowly and you do decide to filter through, keep the speed differential down to a manageable 20 km/h. Watch for any clues of sudden lane changes - looking at mirrors (dont believe theyll spot you); a slight shift in direction; hands changing position on the steering wheel, even a fractional movement of a front wheel.
Move around so your headlight can catch drivers attention and always have an escape route. Be ready for an instantaneous dab of rear brake to scrub off speed, you can usually do it a fraction faster than applying the front (but do use both).