Safe Road Positioning for Cyclists

Rule number one for road positioning on a bike is - never hug the kerb.
 
Many less assertive cyclists worry that being further out from the kerb will put them in the way of traffic, and make them unsafe. It wont. A cyclist is part of the traffic, so being in the stream of traffic helps them to be treated like traffic.

 

Reducing the Risk

Riding in or near to the gutter leaves space on your right for cars to squeeze through, increasing the likelyhood of a vehicle passing inches from your right elbow.
In the gutter you have to contend with drains, cambered surfaces, potentially slippy road markings, litter and other debris like broken glass swept to the side of the road by passing cars.
Next to the kerb you are less likely to be seen by drivers. Drivers look where their vehicle will be in the next few seconds i.e. directly ahead. They pay less attention to their peripheral vision - and if you are in the gutter then you are in a driver's peripheral vision.
Another consideration is maneuverability. Riding in the gutter makes it more likely that you will get boxed in when wanting to overtake parked vehicles, or turn right.

The Highway Code (Rule 163) obliges drivers to give "at least as much space as a car" when they overtake cyclists. By riding further out from the kerb you are forcing overtaking traffic to move further out, giving you more room. Drivers face a 3 point penalty on their licence for passing too close.

How Far From the Edge?

Normally you will be a metre, or more, from the kerb. Rather than think about how far from the kerb, it is better to think of your position relative to the traffic stream on the road, that is, where vehicles are actually driving in the traffic lane.

There are two positions to choose from relative to the traffic stream:
The first, often referred to as the "Primary Position", is the centre of the lane in which you are riding. This allows you to be seen more easily and is the best way of deterring unsafe passes. The primary position is best suited to slower urban roads.
The second, often referred to as the "Secondary Position", is to position yourself about a metre to the left of the traffic stream as long as that doesn't bring you too close to the gutter. This position gives you room to manoeuvre and still offers a good degree of visibility. This position is better suited for faster roads.

And When the Road Changes?

Here are a few suggestions on safe road positioning when the road changes:

Road Narrows SignTake the Primary Position when the road narrows or there is a pinch point.

Traffic Lights SignTake the Primary Position when approaching Traffic Lights. This deters vehicles from pulling alongside of you, and forcing you into the gutter when the lights change to green.

Roundabout SignTake the Primary Position when nearing and approaching a roundabout.