So as 2000 cyclists ride to parliament last night and our MP’s spend 3 hours today discussing cycle safety (or the lack of) in the UK, I still believe strongly that it’s the road junctions that are the major problem with bicycle transport in this country. Get the junctions right, and everything else falls into place.

If you look at a typical through route or “main road” in London, you’ll spot some common characteristics:

• Four lane road (16m) running between pavements (4-6m) lined with shops or other buildings.
• On street parking often filling nearside lane.
• Bus route sometimes with dedicated bus lane with stops either within nearside lane or in pull in.
• Day time restrictions on parking.

When it comes to junctions along these roads, they usually look something like the illustration below and offer limited provisions for cyclists and pedestrians, prioritising motor traffic over everything else.

Traffic tends to get divided into two lanes before the junction allowing plenty of space for stacking up the traffic at a red signal. Stacking is one of these things that looks good on paper, requiring less space in the run up to the junction than a single lane and allowing twice as much traffic through a single signal phase, but has some less obvious disadvantages like the creation of an overtaking opportunity (and thus speed increase) across the junction and conflicts during merging back down to a single lane after the junction.

If we look at the traffic flows across this junction, typically the lights will be sequenced into 3 phases; a main traffic flow phase that is the default phase, a cross traffic flow phase that is triggered by timer or by the presence of waiting vehicles, and an all-way pedestrian only phase triggered by request buttons.

Left/right turns can happen at any time, with right turns giving way to oncoming traffic (and blocking the outer lane) and sometimes helped with a turn filter after the oncoming traffic has been halted.

So lets see what that main traffic phase looks like for vehicles and cycles:

Wow, that’s a lot of potential traffic movement just in this one traffic light phase. Every time a blue line crosses another blue line, that’s a potential conflict point, somewhere where one vehicle can come into contact with another. If that first vehicle is a truck and the second is a bicycle… well we all know the outcome of that dangerous mix.

This is the sort of thing that really puts people off of cycling, things that seem simple to experienced or brave cyclists like crossing two lanes of traffic to turn right at a junction are a solid barrier to the majority of people who want to use their bicycle as transport.

So how can we make junctions like this safer and easier for cyclists (and pedestrians)? Below is an animation of the same cross road junction but with the road space redistributed into a fairer and safer configuration.

What we’ve done is move the curb out into the carriageway to create a buffered cycleway along each existing curb, we then infill the gap with a smooth surface for cycling upon. At the corners of the junction, we continue the new curb to create a buffered corner that protects waiting cyclists from turning motor traffic.

The animating blue lines show the traffic flow within each of 4 traffic light phases, in fact each phase is identical, just turned through 90 degrees. You’ll notice a number of things with the light phasing:

• We no longer have motor vehicles stacking at the lights, one lane goes in one direction.
• Motor vehicles, bicycles and pedestrians can all travel across the junction from one direction at the same time, removing any time benefit being given to any particular mode and removing turn conflicts.
• Due to space limitations, straight forward and right turn lanes for motor vehicles are combined.
• Right turning bicycles and pedestrians have two crossing to make, but the ordering of the phases means the green phases for these crossings follow on one after the other.
• Left turns from the previous direction are combined into the one phase without effecting other movements.

As we can see from the illustration, whereas before we had many conflict points between motor vehicles and cyclists, now we have removed all conflict points other than two between cyclists and pedestrians at the pedestrian crossings and as we know from experience, conflicts between cyclists and pedestrians are less to worry about and easier to overcome.

I’ve spoken before a little about these sort of junctions before.

The obvious problem with this phasing is the reduction in capacity introduced by only have a single direction of traffic moving at one time. This isn’t ideal but can be fixed by separating the straight on and right turn lanes as long as there is road space to do so.

Now we still have 4 phases, but we get distinct straight on and turn phases, allowing us to have long straight on phases if required to keep the main route flowing.

You’ll notice however that we haven’t lost the protected nature of the junction. This is down to not just the physical separation of cyclists and pedestrians from motor vehicles, but the separation of them in time. Restricting movement of all modes to align them in space and time provides for a safe environment where conflict is removed.

This plan of course is not perfect, ideally we’d provide more space between the cycleway and the main carriageway so as to create a buffer that can be used by crossing pedestrians and waiting cyclists, while shielding both from the proximity of moving vehicles and providing a clue to drivers of their intended actions as they move into it. The advantage of this plan is that the existing pavement and curbing can stay as is and makes good use of the available space.