Pedestrianise London

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Bi-directional vs Single Direction Cycleways

Presuming we all agree that cycle tracks are a good thing along main roads with high (>2000 CPU/day) motor traffic volumes (which I think we do), then we need to decide whether we’d prefer two single direction cycle tracks on each side of the roadway, or one bi-directional cycle track on one side of the roadway.

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Visualisation of the Mayor’s cycling vision along Blackfriars Road.

Let’s spend 5 minutes looking at the pros and cons of bi-directional cycleways and at when the Dutch use them. Let’s start with the positives:

  • They take up less road-space than two single direction cycleways. You can get away with less width as you don’t need as much curbing or buffer space, plus they can help with tidal flows.
  • There’s less to build and maintain, you have half as much to sweep.
  • Depending on the roadway in question you could have less junctions to deal with, if you have many turnings on one side of the road, running a bi-directional cycleway on the opposite side so as to save on conflicts might be a good idea.

And the negatives:

  • Conflict points with side roads are more dangerous as bicycles will be travelling counter to normal traffic flow. The solution is to buffer the cycleway from the roadway with a cars length (5 metres) to provide a turning refuge, but this adds effective width to the overall required space.
  • Can make entry and exit points of the track awkward as bicycles have to cross the roadway to gain access to the cycleway. Running the cycleway for the complete length of a route removes this problem but can cause abnormal stage requirements at the junctions either end.
  • Danger of head to head cycle collisions.

So with that all said, which is best?

As always, it depends on context. If we look at what the Dutch say and do we can see that they prefer single direction cycle tracks within urban environments and on distributor roads where conflict with motor and pedestrian traffic is more likely.

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The inner ring road in Amsterdam has single direction tracks on each side.

Out of town and on larger through routes where side road turnings are prohibited/minimised, the comfort of bi-directional tracks wins out.

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A rural through route with a separate bi-directional cycleway in Drenthe.

If we transfer this to a London context we would come to the conclusion that for example, running a bi-directional track along the Embankment is probably the best solution due to the “completeness” of the route and the lack of side turns on the river side.

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Visualisation of the Mayor’s cycling vision of Victoria Embankment.

Whereas the Torrington Place/Tavistock Square cycle route or the Theobalds Road/Clerkenwell Road/Old Street route are probably better suited to single direction cycle tracks due to the number of interaction points with pedestrians and turning motor vehicles.

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Images of Clerkenwell Road and Torrington Place courtesy of Google Street View

As always, it’s the right solution for the right situation, there’s no one size fits all solution, you have to look at the bigger picture and look at the road network as a whole, not just at the section or junction in question.

This image of the ubiquitous urban Dutch roundabout with protected cycleway (and footway) taken from an excellent high up vantage point has been used on a number of cycle blogs, I believe originally from the LCC site. There are a few subtlties of the design, so I’ve taken a few moments to annotate it, as well as flip it left/right so that it’s more intuitive for a UK audience.

This image of the ubiquitous urban Dutch roundabout with protected cycleway (and footway) taken from an excellent high up vantage point has been used on a number of cycle blogs, I believe originally from the LCC site. There are a few subtlties of the design, so I’ve taken a few moments to annotate it, as well as flip it left/right so that it’s more intuitive for a UK audience.

The TFL 2-stage turn

Something new turned up from TFL yesterday, an animation of the design of an “innovative” new right turn layout. In Copenhagen they have “the jug handle”, the Dutch have “the curb protected junction”, now in the UK we have “the confusing mess”.

Mark Treasure has a good look at what’s wrong with it here and I think it’s easy to see the faults in this poor implementation, but more interesting than the “what”, in my opinion is the “why”. How did this solution even get onto the table? Let me hazard a guess.

The problem that TFL are trying to solve is how to enable cyclists to turn right without having to cross two lanes of fast moving traffic by introducing a two stage turn. In other words, how can we get bikes from the cycleway into the ASL box for the perpendicular direction?

The easiest way is to simply allow cycles to pull left from the cycleway into the ASL, the problem with this idea is that missing from the TFL animation is the pedestrian crossing that will exist between the cycleway and the ASL. When the bikes are on the cycleway and wanting to pull into the ASL, pedestrians will have a green man to get into the pedestrian cage in the middle of the road.

DfT rules don’t allow sub-conflicts at a light controlled intersection, that is you can’t give a go signal to pedestrians at the same time as allowing bikes or cars to turn through them for example.

So we can’t possibly allow bikes to just pull through the pedestrians green man into the ASL, we must find another way.

Since the pedestrian crossing on the other side of the road will be red unless activated by a pedestrian, we can allow bikes to turn left and then immediately right through the central reservation straight into the ASL.

Better, but again we’ve introduced a sub-conflict, a minor one but one that could be considered a problem. To get through the central reservation bikes have to swing right, a movement that drivers wouldn’t be expecting and something probably decided as being too dangerous.

So on to option C, the TFL option. Using the DfT’s cycle provision get out clause, the “shared use pavement” to get around the disallowed sub-conflict between bikes and pedestrians. Job done.

Although I’d like to have cheerier news, as far as I can tell, this mess of a design isn’t really the fault of TFL. They’ve tried to do something like the CPH jug handle but due to the rules have ended up tied in knots. The real issue is not how poor this design is, but how to get the DfT to review the rules around sub-conflicts.

That said, I’m not entirely sure why the Southampton jug handle design wasn’t considered, it doesn’t have any of the sub-conflict issues. Maybe the extra space required for it isn’t easy to come by, after all two pieces of drop curb are cheaper than moving pedestrian crossings around.

Of course, the best solution would be a full Dutch style junction.

Terminology

I wanted to quickly talk about terminology. The first Cycle Embassy workshop I attended we had a discussion about the naming of places for bikes, that is cycle paths, cycle tracks, cycle lanes, etc. etc. and what these terms actually mean, there’s a lot of confusion even between the group of us who thought we knew what we were on about. I think we decided we had more important things to talk about, gave up and moved on.

The other day, Two Wheels Good posted a blog post that got me thinking about this again. In it George looked to define two London cycling terms that Boris put in his Cycling Vision, and I think he’s spot on with these succinct definitions:

Cycle Superhighway = completely physically separated from motor traffic + wide enough to accommodate the amount of Londoners who would want to use it.

Quietway = a well-surfaced road with no through-traffic + a 20mph speed limit.

This then reminded me of a tweet by Schrödinger’s Cat:

When I started writing this blog, I took a concious effort to not use the terms cycle path or cycle track. No one really knows what they are. According to the law, a cycle path is anything that it is legal to ride a bike on, so a road is a cycle path, so is a mandatory cycle lane and a cycle track. A cycle track is a cycle path that is separate from the roadway for motorised traffic (and presumably also from the footway).

I prefer to avoid any potential confusion and to use three simple terms which we can all agree upon.

Pedestrians walk on a pavement (or a sidewalk), although it could said that a pavement is only a pavement if it runs alongside a carriageway. Whereas a footway is a right of way for people on foot no matter which way you look at it.

Since a “road” could be the entire road from building to building, and carriageway legally means the whole road that can be traversed along, including the pavement. I’d like to use motorway but we already use that to mean something else, so instead we can use the term roadway to mean the space that motor vehicles use within a road.

And so similarly, the term cycle path or track can be confusing, whereas a cycleway conjurers the idea of not only a separate space for cycling but a kind of motorway for bicycles, something high quality.

You might not think that terminology is important, but it is, if we are to share ideas and talk about common concepts, it’s vital that we have a common language and know we’re all talking about the same thing. This saves us from constantly having to explain what we mean. Hopefully when you and I think of a cycleway it’s the same thing, something a little bit like the example above.

Shared Use Pavement, Dutch Style

In the UK we can easily divide our roads into two types, those flanked by a segregated space for walkers (that’ll be what we call the pavement) and those without.

It tends to be that roads within towns and villages have a pavement, but once you are out into the pieces in between, the pavement vanishes as the distances are too great for people to be walking, this is the territory of the car and the bus. And people on bicycles.

This makes sense right? Where we have places that people would want to walk between, we build pavements, where no one would ever expect to be walking, we don’t. There is nothing wrong with this logic.

The problem comes when you then try to fit the “kinda like a vehicle, kinda bit like a pedestrian” bicycle into the scene (an “augmented pedestrian” so to speak, a pedestrian++). Where do you put them? The answer according to the UK appears to be, mostly on the road but sometimes on the pavement, unless there isn’t a pavement, then you just ignore them and hope they go away.

So let’s look at what they do the other side of the North Sea. They define three types of way-fare, roadway, cycleway and footway, mixing and matching the three as required.

Just roadway

So here we have a country road with no dedicated space for anyone, everyone must share the space equally. The difference to the UK picture is that this is a local road that isn’t a main route and that when it enters the village it is visually narrowed by the suggestion lines and colour treatment.

Perhaps not a fair comparison, but let’s move on and see why.

Roadway and cycleway but no footway

Here is a more major through road. This time however cyclists get their own bi-directional cycleway on one side of the roadway, but since there number of pedestrians and cyclists will be small out here, walkers have to walk in the cycleway until a walkway re-appears nearer to where pedestrian volumes are higher.

Here’s another example in a more built up area. Again we have no separate pavement just a bi-directional cycleway separated from the roadway by a hedge. Properties along the road open onto the cycleway allowing it to be used by residents to get to nearby places on foot.

Road with pavement

Next up we have a shared roadway and cycleway but with a separate footway. This is common on access roads to houses which have slightly higher traffic volume. In the example above, the road only goes to these houses for motor vehicles but is a main bicycle through route, so a dedicated space for walking is a good thing to have.

Roadway, cycleway and footway

Finally we have an example of a totally segregated street, we have a roadway (far left), a cycleway and a footway. Each mode has their own space as we approach a busy intersection (you can just make out the roundabout in the distance) which not only has motor and bicycle traffic movements to worry about but also pedestrian access to the cafes and shops along the street.

What I’m trying to demonstrate with these words and pictures is that the cycleway isn’t part of the roadway or part of the footway, it’s its own space with its own identity as a mini-road just for non-motorised traffic. Sometimes is has a separate footway, other times it doesn’t, but either way, it’s always a cycleway to cycleway standards, not a pavement with a blue bike sign attached as an afterthought/quick win. This is what you need if you want to build bicycle (and to a lesser degree pedestrian) infrastructure that makes a difference and that people will use.

In the UK we have a hate/hate relationship with what we call “shared use pavement”, aka combined foot and cycleways. Pedestrians hate them because they think they’re being invaded by bikes, cyclists hate them cos they’re poorly surfaced, inconsistent and lack priority. I expect however that road planners love them as they’re an easy way to tick the cyclist box without doing any real work.

Rural parallel road for use by foot, bike, moped and tractor

If we look at the Dutch approach we see that “shared use” is actually a cycleway that doesn’t have a dedicated footway alongside (pedestrians can always use a cycleway unless there is a corresponding footway which they must use instead). But we also see that these types of facilities are only ever used in low volume areas and with plenty of width (often as a parallel road that can be used by farm/local motor traffic too).

As always, it’s the right tool for the right job, there’s nothing wrong with sharing space between modes as long as the volume and relative speed of those modes is low, or perhaps more importantly, comfortable.

A sign on a wall in Rotterdam reminding people to keep it gezellig

The Dutch have a wonderful word, gezellig, it’s hard to translate, there’s no direct translation into English, it means something encompassing cozy, friendly, and comfortable, but also good times with friends and general togetherness. It is the philosophy behind Dutch culture, an evening in a nice pub with friends is gezellig, while being at home alone isn’t, although your home might be gezellig, but it’d be more so if your friends were round to visit. However the Dutch don’t just apply it to cafes and houses, but to all sorts of things, including I imagine the road network. If you are to make cycling an easy choice for people, it needs to be gezellig.

This is something we need to learn in the UK. We tend to give ourselves just the two options, roads with pavements in town, roads without in the countryside, and stick the cyclists on the road or the pavement or both. Whereas really we need to not be so narrow with our choices, sometimes an access road with a single surface that everyone shares is the right choice, other times it’s total separation of modes by curbs and verges, it all depends on the conditions in question, not whether the road is urban or rural.

Keep it gezellig Britain.

Small Traffic Controlled Junctions

A number of weeks ago, I was sitting with a collective of smart masses (John Dales of Urban Movement, Phil Jones of Phil Jones Associates, Caroline Russell and Tom Platt of Living Streets, Mark Treasure of the Cycling Embassy, some guys from TFL and Brian Deegan of Camden Council) to exchange information and thoughts on cycle infrastructure at signal controlled junctions. While running through how the Dutch handle conflicts between pedestrians, bicycles and motor traffic at traffic controlled junctions, Caroline asked me (to paraphrase) something along the lines of “but what do they do when there’s not enough room for dedicated turn lanes?”. To which I responded something about the Dutch never having signalised turning motor traffic crossing bikes or pedestrians and that they either find space or remove an arm of the junction to remove these potential conflicts.

That all sounds good in theory, but turns out not to be the truth. Just goes to show the danger of looking at the way things are done in certain areas/conditions and presuming they are the only way things are done everywhere.

My experience is mostly in and around Rotterdam, the port city in South Holland that was rebuilt after the war with wide American style boulevards which have since been retrofitted with cycle tracks. In Rotterdam there is the space to have dedicated turn lanes so that conflicts between turning motor traffic and bicycles going straight ahead are avoided.

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Out of the city in the countryside there is room to provide full segregation, while in cities like Amsterdam where space is absolutely at a premium, the solution has often been to remove motor traffic altogether either through road closures or by banning certain traffic movements.

A few weeks later after our chat, I was in Noord Brabant on holiday with my family, this is the central southern province of the Netherlands about a hours drive south of Rotterdam. While in the city of Breda, I was able to look at smaller traffic controlled junctions in action.

Once back in London I was able to double check the Dutch cycle infrastructure bible, The Crow Manual for Bicycle Traffic, to see what it says and what I missed on previous readings. Sure enough, when it comes to turning traffic, these turning conflicts should ideally be removed, but the manual does go on to give advice on alternative options in a kind of hierarchy of provision. The trick I missed out on is that the manual doesn’t differentiate between treatments for signalised versus right of way turns, both are treated with the same brush strokes.

Let’s look at the three options:

Dedicated turning stage

So this is the ideal solution, the solution that I’ve talked about before and is shown above.

It gives total modal separation, there are no conflicts between motor traffic and bikes or pedestrians as the movements of each mode is synchronised to occur at the same time.

The downside is that it requires space for turn lanes for motor traffic, so for a cross road at a minimum you need 3 lanes on each arm (but only one exit lane) plus space for cycle tracks and pavement, space which often doesn’t exist (a t-junction only requires 2 lanes).

Cycle track bends away from motor carriageway

Next in the hierarchy, if we have no space for a full junction and we can’t close off a junction arm to motor traffic, then if there’s room we should move the cycle track and pavement away from the junction so that we create a buffer between turning motor vehicles and the potential conflict point.

So not only are bicycles and pedestrians protected from left turning cars by a curb, but the curb is large enough to force cars to move slowly and to cross the bikeway and footway at 90 degrees, increasing visibility and thus safety.

The only thing we need are markings to make sure that turning vehicles give way to bikes and pedestrians going straight on. This is where things get weird from a UK point of view.

In the Netherlands turning vehicles have to yield to vehicles going straight on that they might be crossing, so for example, a car turning left must yield to pedestrians crossing that arm of the junction (technically we have this in the UK too, highway code rule #170 but with combination of traffic signals it is rarely observed or expected). They accomplish this awareness by using the zebra markings and elephant feet (big white squares, like a zebra with a gap down the middle) markings, they also sometimes add the give way chevrons when it’s deemed necessary.

imageChoices choices, KFC or McDonalds? This image is of a large urban junction, but the markings are the same and demonstrate the point.

Here in the UK we have no precedent for this, in the above drawing I have used zebra style markings although they’d be used in combination with the crossing signals, so they’re not really a zebra crossing at all. Opinions appeared to be divided as to whether this would be a legal or sensible set up or if some other new style of marking would be required.

An alternative would be to replace these right of way crossings with signals so that turning motor vehicles get a red signal after the turn, although this could lower the capacity of the junction if the turn is popular (as usual there’s no one size fits all solution).

Cycle track close to motor carriageway

Often however, there isn’t even room for this bending awaywards of the cycleway, so instead we should bend it close to the main carriageway so as to improve visibility.

Here we have a main route running top to bottom, meeting a local road going left to right which has cycle lanes rather than curb separated cycle tracks (just to demonstrate both cases, it’d be better if we introduced cycle tracks before the junction on these approaches too).

As you can see, the cycle tracks are put into a position where there are no obstructions between them and the main carriageway and then marked across the junction where the possible conflicts can occur. We’ve even managed to squeeze in a little waiting space for people to do a two stage (jug handle) right turn.

If there’s room then we might do a hybrid half and half solution, something like the following.

So this is how the Dutch handle small traffic controlled junctions with cycle provision. The issue for the UK are two fold:

Pedestrian green man

We have a requirement for when pedestrians have a green man not to have turning traffic having to give way to those crossing. This is the common way of doing things on the continent and in America (in fact I can’t think of another country other than Ireland that has this requirement) and means that we can have very simple light stages for these small junctions; everyone goes north/south, followed by everyone goes east/west, with turning traffic giving way to anyone going straight on. This makes for a very efficient and very understandable junction organisation.

The problem here is that we can’t currently legally have vehicles with a green signal giving way to pedestrians who also have a green signal. A proposal would be to adopt what they have in the Netherlands and other places and use a type of zebra markings on the pedestrian crossing so enforce the need to give way to anyone on the crossing. This then causes another problem with having a zebra with pedestrian signals… this isn’t going to be an easy nut to crack.

Cycle lane/track across junction

We have an elephant foot marking in the UK, but they are limited in use and don’t have the same meaning as those in the Netherlands. Here’s the relevant blurb from the DFT:

The marking known as elephant’s footprints, formerly shown on working drawing WBM 294 and in LTN 1/86, cannot be used without approval from the Overseeing Organisation. Authorisation will only be given where cyclists cross under the protection of traffic signals and the special marking is necessary because cyclists’ route through the junction would not otherwise be obvious.

So the elephant’s footprint markings are not for the attention of motor traffic but are to guide cyclists across the junction (and they can only be used where there are traffic signals).

Again this is a similar problem to that above with the pedestrians. If elephant’s feet can only be used with “the protection of signals”, then having a turning motor vehicle and a non-turning cyclist both having a green signal would not appear to be covered by this, and the use of give way markings (like on a zebra crossing) isn’t mentioned.

So a proposal would be to get a change to how elephant’s footprints can be used to allow them to be used in conjunction with give way markings (the single line wide dashed markings like on a zebra crossing).

Conclusion

So in conclusion, when it comes to small urban junctions that need to have traffic signals, the Dutch solution is to forgo the safety of having isolated turn stages and the movement of the cycleway away from the roadway, but only as a last resort.

In order to do this in the UK we’d need two things adjusted in current DFT guidelines (someone who knows about such things will check that I’m not talking rubbish here). We’d need to allow turning vehicles to “mingle” with crossing pedestrians and bikes (a toucan/zebra hybrid, toubra or zebcan if you will), and to give elephant footprint markings the same status as zebra markings so they can be combined with give way markings (and used without signals).

Love Twickenham, Go Dutch (Part 2)

This is the second part of my look at applying the principles of Sustainable Safety to Twickenham town centre. Go refresh your mind of part one.

Previously on Pedestrianise London.

Back in October last year I started to look at how the Twickenham Area Action Plan might look if it were put together by the Dutch. We looked at how the streets of the town are used, how they should be prioritised to reduce unwanted behaviour and encourage a positive environment.

Since that time, the borough council have pushed ahead with the plan which has now moved into a more detailed phase after it’s initial consultation. So let’s do the same and look at how, following on from part one, we’d design the region based around the principles of Sustainable Safety.

A quick recap. Here’s the lay of the land. We have the main north/south through route of London Road into King Street into Cross Deep (blue), and the east/west distributor route of Richmond Road to Heath Road (orange), with property access roads in green and pedestrian/cycle only in red.

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So here we go, a detailed plan for the town from yours truly…

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Let’s go in for a good look at the details.

Twickenham Station

Starting from the north end of town, the station is a critical link. It not only brings people to the town but also rugby fans to the stadium on match days, so it has to not only have all the usual train station type stuff, but also be suitable for handling the masses.

The traffic light controlled t-junction between London Road and Whitton Road is currently designed to aid the flow of traffic from the two roads heading towards town. Since it is in effect a fork in the road, it is an ideal candidate for a three pronged roundabout. Whitton Road is also a good candidate for closing to through traffic to the A316 since it is a narrow road and this function is already adequately carried out by London Road.

We have chosen to completely close the entrances to Cole Park Road and March Road to motor vehicles so as to simplify the road layout by removing these unnecessary junctions since these access roads are already accessible by alternative routes.

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London Road heading south towards town is currently a 3 lane road with a bus lane heading south and a cycle lane that’s mostly used by buses heading north. Removal of this underutilised space along with removal of the central reservation creates room for wider pavements and cycle tracks that run behind the bus stop pull ins.

The pelican crossing has been replaced with a single stage zebra positioned outside of the station entrance and between the bus stops allowing easy transfer from train to bus.

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Arragon Road

At the beginning of the London Road shopping area we re-direct traffic off of London Road and down Arragon Road thus freeing up London Road to be an access only space that will be more pleasant for pedestrians and the shops that run along both sides of the street.

At the junction with the priority changed, we have removed the existing traffic lights (and the race to get onto the bridge over the railway first that came with those lights) and replaced them with a single lane roundabout with central and corner “truck aprons” to allow for the wide turning angles of buses and delivery trucks. Due to space and the legal size requirements of roundabouts, this would actually technically be a large mini-roundabout, ie. a roundabout without a central curbed area, but with the truck apron acting as a de-facto curb.

With the south portion of London Road becoming a pedestrianised zone, it can be repaved with an attractive tactile surface and made pedestrian and cyclist friendly. Alterations to the bus routes would now take northbound buses up this portion of London Road via the southern bus only entrance, while southbound go via Arragon Road.

The roundabout could be done without and the junction treated as a pure right of way junction, but the roundabout helps reduce vehicle speed and so helps with the pedestrian and cycle crossings.

Along Arragon road, a bi-directional cycle track has been added to the north side. Although bi-directional paths are usually to be avoided in urban areas, in this case it is safe and worthwhile as it simplifies the junction with Amyand Park Road, provides better access to the primary school, and since the south side of the road simply runs around the multi-story car park there is no required access there for people on bikes or on foot. Having a bi-directional track also helps us optimise space and keep room for on-street parking.

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Richmond Road

Where Arragon Road meets Richmond Road and becomes York Street we keep the traffic signals but again rework the junction to improve cyclist safety and pedestrian crossing times.

We have a cross roads but not enough road width to give each turn it’s own traffic lane, so we need to either combine or remove some turns. We can’t easily remove any, so we’ve had to combine some together which gives us two choices:

  • Either we have to inconvenience cyclists and pedestrians by making them wait while motor traffic for the combined turns get a green;
  • Or make sure that the cycle track comes close to the roadway so it is obvious that cycles may be present and that the roadway crosses the cycle track.

As we have the end of a bi-directional cycle track to deal with which adds the requirement of additional crossings, we’ll be best to stick with the first option.

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The light stages are shown below, they should be triggered by detection loops and/or push buttons and should be flexible, for example the third stage could combine parts of the second stage to allow left turning motor vehicles from York Street if there are no crossing pedestrians.

If we went with the second option, the cycle track across south side of Arragon Road should be kept close to the roadway and a warning sign should be included for turning traffic. Of course, there is no suitable sign in the UK, here’s how the Dutch do it.

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"Let op" literally "Look out". Note the flashing orange turn signal and the warning sign below, the cycle track in question is to the right beyond the bushes slightly out of view. Picture courtesy of Google Streetview.

London Rd / King St / York St / Church St

The heart of town is this main junction between the two main routes at the intersection of the three main shopping streets.

Since we want to encourage people into this area, we want to reclaim this area from the traffic heavy junction it is currently. The best way to do this is to remove the traffic junction entirely. So we’ve closed this end of London Road to through motor traffic traffic except for buses coming from King Street while keeping it open to cyclists and pedestrians.

We’ve also added two sets toucan crossings to King St / York St to allow people to cross between London Road and Church Street. These could be zebra crossings depending on traffic speed and volume, and if so a central island refuge could be added to aid crossing, although it would need to be wide enough to fit a bicycle.

The entrance to Church Street has been constrained to humanise it with a tight corner radius, a steep vertical curb deflection, and tactile pavement-like surface; although in practice we could remove it altogether to create a larger pedestrian space and remove any potential conflict since it’s accessible from Richmond Road.

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Cross Deep

Along the full length of King Street we have included cycle tracks that run behind the disabled parking, loading bays and bus stops.

At the far end of King Street we have the Cross Deep junction. Due to space restrictions we’ve stuck with a set of traffic lights rather than install a roundabout, however we’ve made some changes to the three lane confusion that currently exists.

We simplify the lane arrangement to a two lane entrance and one lane exit for each aspect of the t-junction. This allows us to synchronise the traffic movements of each mode (motor traffic, bikes, and pedestrians) together into the same stages (all right turns go together, etc. I inadvertently spoke a little about this junction last post) so as to make for a safe yet efficient junction.

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Conclusion

So there we go, my take on how the council could revitalise and revolutionise our town centre through inclusive street design inspired by our friends across the North Sea.

Now I’m not a traffic engineer, but as far as I understand all the things I’ve mentioned are possible within current legislation, so the only real barrier is political will. Plus nothing here is specific to Twickenham, we can apply these and similar techniques to any town or village to re-shift the balance back towards a people friendly environment.

Of course, taking the risk of reducing capacity for road vehicles would be a brave one, politically, but there’s only so much space in our towns and all evidence points to the fact that traffic always grows or shrinks to fill the available space as long as you provide people with quality alternatives (a phenomenon known as traffic evaporation). Some day we’re going to have to have these decisions forced upon us, perhaps it’s time to start getting prepared?

Phases Set To Stun

Mr Phil Jones let me know that when I used term “phase”, I should have been saying “stage”, so I’ve updated the content below as such, but since my “witty” play on the word “phasers” wouldn’t work I’ve left the post title as is. Please excuse my artistic license.

With the Mayor’s excellent Cycling Vision comes the inevitable chatter about “bicycle phases through traffic lights” and how the inclusion of bicycles into junction design will negatively effect stage timings.

There seems to be a school of thought that by providing for bicycles at junctions, you need to provide a dedicated bicycle phase in a similar ilk to the way pedestrian stages are handled in the UK. However this isn’t the case. I’ve talked of this before so I’ll try not to repeat myself too much.

Let’s look at the details via some lovely diagrams, first up how a standard UK crossroad junction is staged up.

In the following, blue is our motor traffic, green our bicycle traffic, and yellow our pedestrian traffic. Each frame of the diagram shows the movements allowed in a stage of a standard crossroad junction. Arrow heads show movement direction, while crossbar heads show waiting at a red signal.

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  1. In the first stage  traffic flows freely north/south and can turn east/west from both directions at will by giving way to traffic from the opposite direction. Bicycle traffic is mixed in with motor traffic and expected to blend seamlessly with motor traffic movements, while pedestrians are halted from making any movements other than turning the corner they are already on or crossing to a mid-carriageway refuge.
  2. The second stage is just like the first but for the east/west direction.
  3. The third and final stage is an all green pedestrian crossing phase. We stop all motor and bike traffic from all directions and allow the pedestrians to go crazy, but realistically we only give them enough time to cross a single roadway.

We apply the same treatment to t-junctions too, except that left turns from the straight ahead route can turn in both motor traffic stages  Below is an image of a typical t-junction curtsey of Google Street View, in fact this is a junction I know well as it’s in my home town of Twickenham.

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Now let’s look at a better, fairer, safer, but still efficient way of staging our junction (aka what they do in the Netherlands).

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The first thing you’ll notice, we have 4 stages instead of 3, but the difference is that in each stage we have separation of vehicle movements by type. The only potential conflicts are between cyclists and pedestrians, a conflict type that has proved to be manageable by both parties (depending on volume).

We have two straight on stages where motor vehicles, bicycles and pedestrians all get a green light, but all motor vehicle turning is prohibited.

Each is followed by a turning stage where left and right motor vehicles turns go together, while bikes and pedestrians are only allowed left turns. To do a right turn, you go straight on in the straight on stage and then wait for the transposing straight on phase to complete the turn. Not ideal, but safe, easy, and the stage sequence can always be optimised for common turn directions.

The turning stages can be skipped if nothing is detected by inroad detectors or pedestrian push buttons.

This setup removes all the dangerous conflicts from the junction as well as removing the usual UK ambiguity of combined straight ahead and turn lanes which cause their own conflict and confusion.

The negatives are of course that to separate vehicle movements we need to separate vehicles that want to go in each direction. As such we need a traffic lane per direction, something which could be problematic is space is at a premium although there might be more than we’d expect since we can do away with large pedestrian refuges.

Via the magic of digital manipulation, let’s see how this might look if we were to apply it to our Twickenham junction above.

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As you can see, on our approach we’ve split the turning motor traffic into two lanes, and while the left turning traffic is held at a red signal, bikes on the red cycleway and pedestrians on the pavement also have a green signal for turning right via the toucan crossing going straight across the road to the cycleway and pavement on the opposite side. 

Note that the cycleway carries on past the motor traffic stop line and through the pedestrian crossing (priority here would depend on volume and controlled via a zebra/give way setup) and is far advanced in line with the pedestrian crossing of the east/west roadway. This not only provides a safe place for bicycles to make a right turn from, but also puts them into clear view of left turning motor traffic (which will always have a red light when bicycle traffic has a green).

We’ve separated our varying modes of transport in time and space so as to remove the conflict points, while also providing an efficient junction that gives each mode equal share of green light time.

So let’s hope junctions like this are in the Mayor’s plans for London.

Repeater Traffic Lights

I’ve come across a strange collation that is probably more conjecture than science, but that I think is interesting anyway.

Countries that have low levels of cycling have traffic signals with repeater lights, and those with more cycling do not have repeater lights.

Really? As I said, there’s no scientific data behind this bold claim, just the observations of a transport geek, but maybe there’s something in it. 

So what is a repeater light?

In the UK, traffic lights appear next to a stop line. This stop line is a thick solid white line that stretches across the carriageway and that can only be legally crossed when a green light is shown at one end of the line. In some countries the lights themselves are the marker to stop at (I’m looking at you France), but here we make it nice and simple and have a big white line to show exactly where you have to stop.

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This the best picture I have of UK traffic lights, as you can see the repeater lights opposite the junction allow vehicles to encroach into the junction.

Because of this line and the fact it is the stopping point, we can have something that other countries can not, extra traffic lights that are not where you have to stop but are just there to make sure you see the lights. These are repeater lights. They repeat the intention of a light at a stop line to add more impact and make sure we notice that stop light when we’re busy looking the other way.

The UK has repeater lights, so to does Ireland, Australia and New Zealand, the countries in North America (although sometimes they just hang a single light in the middle of the junction, but it’s still beyond the stop line), whereas the other countries of Europe (you know the ones, the ones with more than 2% cycle modal share) all have traffic lights only on the entrance to traffic controlled junctions.

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And this the best picture I have of Dutch traffic lights. The lights are positioned a cars length in front of the stop line meaning you have to stop behind the line to be able to still see the lights.

So why could this correlation be? Who knows? It’s probably just a coincidence, however that’s not to say that there’s not something in repeater lights being a bad thing. Let’s look at the facts…

Repeater lights allow you to still see the lights even once you’re beyond the stop line. Whether you are motorist or cyclist, the repeater light allows you to happily stop within the pedestrian crossing (or ASL, although the less we talk about them the better) and still know when the lights have changed. My experience of driving in countries without repeater lights is that everyone (yes everyone without fail) stops behind the stop line, simply because if they run past it they then can’t see when to go, get beeped by the car behind and feel like a bit of a prat.

So perhaps my point is that it’s not the drivers/cyclists fault that they sometimes progress over the stop line, perhaps it’s the design of the lights themselves.

The 1960’s overzealous requirement to think for the motorist by filling their entire vision with red lights to such an extent that many don’t see the stop line at all, we’ve all seen the poor chap whose somehow managed to get confused and stopped at the repeater light on the exit of the junction much to the mirth and anger of his fellow travellers stuck behind him.

So perhaps it’s time for a change in rules. Now we have LED light technology which removes the possibility of bulb failure, we could do away with the confusing, ugly, cluttering repeater lights and make our traffic controller junctions just that little bit safer for everyone?