Sunday 4 May 2014

The best traffic light solution for cyclists. Simultaneous Green scales to almost any size of junction. Safe, convenient

Imagine if it were possible for cyclists to take their desire line across traffic light junctions, even riding diagonally if that the shortest path. Imagine if this was possible in complete safety because there were never any cars using the junction when cyclists used it. Imagine if cyclists' green traffic lights were twice as frequent as those for drivers so that average delays were shorter if you cycled. Imagine that all this was already reality...

For cyclists, the safest and most convenient design for traffic light junctions is the simultaneous green.

With this design, cyclists always make their maneuvre in one and directly. There are never inconvenient and unsafe two stage turns, never is there the possibility of being "hooked" by motor vehicles turning across a cycle lane between other traffic lanes, never do you have to merge with motor vehicles making the same or other maneuvres and there's never a requirement to find your way forwards to dubious safety of an advanced stop line or to make your way across several lanes before the junction to get into the correct lane to make a turn across traffic.

Simultaneous Green gives cyclists their own green phase during which they may travel in all directions at once, including diagonally, following their own desire line across the junction. While cyclists are crossing, all motor vehicles are held behind red lights. When motor vehicles are moving, all cyclists are held behind red (with the exception of often being able to make a safe right turn).

This video shows one of the largest simultaneous green junctions in action:

This is one of the largest simultaneous green junctions in Groningen. As the video starts, we are about to cross ten lanes of traffic, diagonally. This is maximally convenient for cycling. Note also it takes just 20 seconds for us to cross and clear the junction. That's the time required for everyone to cross in all directions by bicycle in the world's top cycling city at a very large junction. Note also how easy emergency access through the city is aided by the bus lanes

It's obviously convenient. Is it really safe ?
There have been no incidents with
bikes here at all. Note how west and
east sides of the junction are very
different. No single solution fits
all existing streets.
Because these junctions remove cars from the road when cyclists are riding on them, the main danger to cyclists is removed. The result is that cyclists crossing simultaneous green junctions are rarely involved in collisions and even more rarely injured. These are extraordinarily safe junctions for cyclists. Between 2007 and 2012 Only one incident involving a bicycle was reported at all of the simultaneous green junctions in Assen added together and that incident didn't result in an injury.

People sometimes wonder how it is that cyclists don't collide with one another while crossing diagonally. There are actually good reasons for this. The whole area of the crossing can be used and peoples' desire lines don't cross at the same point in time.

It's not mere opinion which leads me to call these safe junctions. There are figures to support this and they show a stark contrast between the impressive safety record of simultaneous green junctions, of which there are many in Assen and Groningen amongst other Dutch towns but at which cyclist injuries are virtually unknown, and the relatively bad safety figures seen at shared space and other less well engineered junction designs. What's more, simultaneous green junctions are also subjectively safe. Who doesn't feel safe to cycle when there are no cars moving ? The result is that this type of junction empowers vulnerable road users rather than dis-empowering them.

The designs of different sides of
junctions like this vary enormously
depending on the road that they
are connected with. The principle
scales to all sizes and works with
mixed arrangements like this. This
is the junction at which there was a
single minor incident reported by
a cyclist in 2008. An incident which
did not result in an injury.
Why isn't everyone asking for this design ?
I've been writing about the benefits of simultaneous green for many years now and we have been demonstrated these junctions to hundreds of people on our study tours but somehow it's not easy to get the superiority of this design over others through to people.

This is a superior way of using junctions but it suffers from a lack of familiarity.

There's no one size fits all design that people can take away. This is not about We show a variety of different sizes of simultaneous green junction but we find that people still find it hard to understand how this scales to all sizes of junctions. Some think it takes a lot of space or takes too much time from other modes. None of these things is true. Simultaneous green principles apply well at all sizes of junctions and we've found that in all cases it works extremely well. What's more, all the junctions we're aware of have great safety records.

How much impact on other modes ?
There also appears to be a perception that safety and convenience for cyclists has been achieved by making the junction inconvenient for other modes. While it's true that these benefits are the result of cyclists having the entire junction to themselves when they cross, it should be remembered that cyclists travelling in all directions at once make the very best use of the space while they do so. Because of this, even very large junctions can be cleared by big groups of cyclists from all directions at once in a very short time. After they're clear, there are no cyclists left on the road who could in any way inconvenience other modes. What's more, drivers don't even have to do so much as cross an empty advanced stop line because there is not reason for there to be an advanced stop line and they do not have to negotiate road space with cyclists either on the lead up to the junction, while crossing or at the other side. For all these reasons, simultaneous green leads to very efficient use of the junction.

This design can give cycling a competitive advantage
Because cyclists' light are completely independent of those used by drivers, more advanced possibilities are on offer than are possible merely by synchronizing with the cycle used for cars. It is often the case that cyclists are given more than one green phase during each cycle of the lights, meaning that the average delay by bike is half that by car. When simultaneous green is combined with being able to make a safe right turn against a red light, which it very often is, the average delay for cyclists, taking all desired directions into account, is reduced even further. This helps to encourage cycling, which itself improves journey times for motorists.

Examples of scaling to all sizes of junctions
While the video above shows one of the very largest simultaneous green junctions, where you ride straight over or diagonally across a ten lane road in Groningen in one movement, the following photos show how the design scales down from this very large junction to work just as effectively at extremely small junctions. Note that each of these examples is of a different design. There is no one-size-fits-all style of concrete buffer required to separate bikes from cars in a simultaneous green junction. No single easily explained design. The principles are what are important, not an exact pattern which won't necessarily fit into your city:

The same junction as shown in the video above. There are ten lanes here. Four in each direction for general traffic and an additional two lanes for buses only in the middle of the car lanes. From the cycle-path on which we approach you can turn left (diagonally) or go straight onwards. Note the right turn lane for cyclists, which takes cyclists around the corner entirely separately from the road and does not require stopping at a red light at all. There is more about this junction in a much older blog post.

Another view of the same junction from a different angle, in which people can be seen riding in all possible directions.  Note that there is no concrete kerb on the corner because this would be in the way.  Everyone on a bike is following their own desire line while all motor traffic is stopped. This removal of the main source of danger at the junction is what makes simultaneous green so safe. This may look lik a composite photo because there are bikes all over the place, but it's not. This is just a still image of the same crossing as shown in the video at the top during a different green phase. Cyclists negotiate routes on simultaneous green junctions, making maximum use of the available space. This is why it's such an efficient design
A wide bidirectional cycle-path leading up to a medium sized simultaneous green junction. This is the same junction for which I showed the accident record above. Right turns, and also left from a position to the right of the photo, are possible here against a red light simply by riding around the corner on the cycle-path.

The same junction from a different angle. The narrower road leading up to the junction from this direction has just an on-road cycle-lane, but safety and convenience are enhanced by a kerb for a short distance before the junction which also assists integration with a simultaneous green junction. The blue sign gives specific notice that right turns are allowed against a red light.

The same junction again, this time from a third angle. In this case, a 2.5 m wide single direction cycle-path leads up to the junction. The corner of this junction which appears on the far left of the photo is that which featured in the first photo. The blue sign shows that right turn on red is allowed here.

A smaller junction and a narrower cycle-path which still allows bidirectional use by cyclists. Right turn on red is accomplished by turning right on the cycle path which goes around the corner to the right just off the edge of the photo.

On the other side of the same road, facing the last photo. This is a very narrow one-way street for cars which has on-road cycle-lanes to allow bidirectional use by bike. A short section of cycle-path is used to provide a waiting area for bikes. Those who wish to make a left / diagonal turn use the left half of the cycle-path. Those going straight on use the right half. Simultaneous green scales easily to small junctions like this. Because cyclists must cross the road to head to the right, right turn on red is not possible in this instance.

At the end of a feeder street in a residential area which has no specific cycle provision at all, this bridge is wide enough to provide a small length of cycle-path which provides safe access and a waiting area for cyclists using the simultaneous green. The cycle-path on the far side of the road is bidirectional so we cross the road to turn either left or right and in both cases cross the road first. In this case, right turn on red is not possible.

A view in the opposite direction from the previous photo. A low traffic road has a short length of on-road cycle-lane which leads into the simultaneous green junction. Right turn on red is possible here simply by joining the cycle-path heading left-right across the photo. A different view of this junction can be seen in an older blog post

The design works even at extremely assymetrical junctions such as this. In this case, we're on the bidirectional cycle-path which runs left to right through the previous photo. When the light goes green, cyclists heading in both directions on this cycle-path may turn across to the other side of the canal (right in this picture), go straight on towards each other remaining on the cycle-path, or turn down the small road in the previous photo (left in this picture). A view of the same cycle-path at the same junction but taken in the opposite direction can be seen in an older blog post
Busting myths
I hope with this blog post to have busted myths about Simultaneous Green being difficult to implement or only being suitable for large junctions. In fact, it works extremely well at all sizes of junction from the very small to the very large.

What's better ?
The only way to improve upon simultaneous green is to remove traffic lights from cyclists' routes altogether. Assen provides a good example of how to design so that traffic light junctions are mostly away from cycle routes. Where cyclists and traffic lights come together, simultaneous green is by far the best solution.

What's worse ?
Almost any other design of traffic light junction creates more problems and danger for cyclists than does this, yet it is these other ideas which are given prominence in design guidelines around the world.

One of the junctions shown
above in Assen looked like
this at the start of 2007.
The "protected intersection"
design which some people
are still pushing.
The much pushed but somewhat mythical "standard Dutch junction" is not a terrible solution but it is less safe and less convenient than simultaneous green.

Copenhagen Left type junctions are not only inconvenient because they require cyclists to stop twice and divert from their desire line to make a turn across traffic but they are lethal in their home country so likely to be lethal in yours too.

Advanced Stop Lines simply don't provide any real protection for cyclists at all and centre of the road cycle lanes which are sometimes used to provide a way to turn across traffic at ASLs encourage cyclists and drivers to cross each others' paths.

Shared Space junctions have far higher injury rates and especially cause problems for the more vulnerable road users.

What happens to pedestrians ?
Light controlled pedestrian crossings
shown in blue on a crossing in
Groningen. Possible directions by
bike from one corner shown in red.
The zebra crossings give pedestrians
priority over cyclists but in most cases
the pedestrian green light does not
not light at the same time as that for
Pedestrians must also be accommodated by any junction design.

It's not practical to allow pedestrians to walk diagonally across at junction at the same time as cyclists are doing the same as this causes conflict. However, provided that pedestrian crossings are outside of the cycle crossings, as shown in the picture on the right, pedestrians can cross in all directions other than diagonal at the same time as cyclists use the simultaneous green crossing and without any conflict at all.

The time taken for a cyclist to cross a wide road is considerably less than that taken by a pedestrian so there is no extra impact on traffic light cycle times from the point of view of motorized modes due to allowing simultaneous green at the same time as pedestrians are allowed to cross.

In Assen, conflict has been removed by
a further step. Pedestrian crossings are
completely outside the cycle crossings,
meaning that there is no conflict at all.
Pedestrians therefore don't need to rely
upon cyclists stopping for zebra
crossings on cycle-paths
In practice it is necessary at wide junctions to provide central reservations with additional push buttons to operate the pedestrian crossing. This is required to accommodate people who walk slowly. That can also be achieved without any conflict though it's never very pleasant to be in the middle of a road. It should never be necessary for a cyclist to cross any road in more than one stage, even if riding diagonally, even if crossing ten lanes of traffic as shown in the video above, because cyclist speeds are higher than pedestrian speeds.

Groningen's simultaneous green crossings use zebra crossings across the cycle-path in an attempt to give pedestrians priority over cyclists. Unfortunately, they placed the pedestrian crossings in front of the cyclist stop lines. The problem with this design is that it can result in a pedestrian reaching the far side of the road just as cyclists are given a green. Cyclists are therefore delayed entering the junction and may be tempted to jump a red light. This potentially converts a minor bike-pedestrian conflict into a more serious bike-car conflict. In Assen a superior design is used which places the pedestrian crossings completely outside the cycle crossings. Therefore cyclists can always go without delay when they have a green light, and pedestrians never clash with cyclists.

Roundabouts ?
In some cases, a roundabout may be more appropriate, but this requires good design. Not all roundabouts are equal. Not even all Dutch roundabouts are equal. Some have extremely good accident records while some do not.

Choose Simultaneous Green
Simultaneous Green is by far the most convenient design of traffic light junctions for cyclists. What can be more convenient than following your desire line across a junction ? This is also now an extensively tested solution which has proven to be extremely safe - this is objectively shown by viewing the online map of collisions. This junction is more convenient and safer than the mythical "standard Dutch junction", much more convenient and very much safer than the proven lethal two stage turn design and it also has also proven to be far safer for cyclists than shared space junctions even when those are on a smaller scale, catering for a much smaller number of motor vehicles.

Dutch signage for
simultaneous green.
Given the advantages and the flexibility of simultaneous green, this is the junction design which cycling organisations the world over should be trying to emulate. It may take some changes to your local laws to allow the required signage and to change to way in which traffic lights are sequenced, but these are human constructs which are changed all the time. The advantages of Simultaneous Green are such that it is truly worth campaigning for.

It's not new (I've been writing about it for six years) and it's not an unproven idea. It's popular with cyclists because of its convenience and has proven to be safe. Enough time has passed that had campaigning for this junction design started when I first wrote about it, your laws could already have been changed to accommodate this style of junction. Get campaigning!

Previous posts about simultaneous green junctions include many videos and photos of other examples.

If you think that six years doesn't sound like much time, remember that it took only eight years for the Netherlands to transform the whole country enough to be inspirational.


Unknown said...

I favor giving people using bikes priority at intersections. Here in Southern California, USA, with the bias toward motor vehicle uses, I'd fear the All-Green phase for bicycling would too likely to be too short, too infrequent, and thereby less convenient/effective for bicycling. :-(
That's why many of us here are leery/fearful of separating out bicycling from general travel lanes; we get "back of the bus"/poorer service in order to keep us out of the way of motor vehicle users. :-(

Jacob Lynn said...

But Unknown, keeping bicycles in the general travel lanes guarantees "back of the bus" quality service for bikes, because it's dangerous and (as importantly) feels that way. I'm in Norcal and I'm not at all leery about requesting segregated bike infrastructure.

Pedal Pusher said...

good stuff.
i suppose it is an extension of the "all-green" pedestrian junctions, such as some in Japan, at least on in the shopping district of Edinburgh, and at least one in Newquay, Cornwall - the last mentioned-two, I have used myself :-)

Unknown said...

David - I think the editing process went wrong in the pedestrians section of the article:
However, provided that pedestrian crossings are outside of the normal pedestrians crossings can operate in all directions at the same time as cyclists are using the simultaneous green crossing.

Stewart B

David Hembrow said...

Stewart: Thank you for your correction. You're right that it made no sense at all as written (though hopefully the picture made clear what was intended). I've corrected and expanded on the text.

HB said...

David, Are there any SG junctions that do allow pedestrians to cross diagonally as well?

David Hembrow said...

HB: I've not seen one where pedestrians can cross diagonally as well and I doubt that it would work well.

While SG junctions decrease conflict between cyclits and other modes, letting pedestrians cross diagonally at the same time would create conflict. It would have all the problems of shared use paths.

What's more, green times would have to be far longer than now, reduced the advantage of SG so far as all modes are concerned.

Pedestrians and cyclists are not the same and should never be treated as such at junctions.

Thedoc said...

This whole A and B thing falls down here and only makes sense if there is only one cyclist going in each direction. If A and B go at the same speed the will avoid each other. The other guys behind them won't though. This is a very site specific type design and you would really struggle to get it to work on a site in London with high cyclist. I am not trying to be negative here but It would take a huge shift in cyclist behaviour here, especially from those going straight ahead to work as they like to get away at speed.

I also worry about peds. You are not going to be able to get a scheme through that holds up traffic for long. A lot of the time he only way to get peds across is by having an all red phase. This is just the the logistics of how it has to be when you have all movements at a junction. You would be asking the peds to cross at the same time as the cyclists and then stop before the cycle track. To be honest I don't have a problem with this providing they have enough storage space but it is how you do this which is he problem.
The zebra isn't ideal as then you are telling cyclists to stop and potentially back up into the junction as the lights go green. Also you can't have mixed crossings like a signal for one part and a zebra for the second. You should be able to but as far as I know it's not allowed.

That means you give the cyclist priority and the peds either cross the track when a gap or wait until the junction is clear of bikes. You would almost have an uncontrolled crossing straight after a signalised crossing. Again you are looking at missing crossing types and also storage for peds in busy areas. I think you would struggle to find the space. Nice design but not practical in many places I fear.

Am just seeing this for the first one though so hope to be proven wrong.

David Hembrow said...

Thedoc: Are you seriously trying to suggest that what works exceptionally well in some of the highest cycling modal share cities in the world will somehow not cope with the far smaller number of cyclists in London ? Of course it will !

This is a remarkably non site-specific design - hence the wide range of different sites of different sizes shown above. The roads crossed by the junctions shown above vary in width all the way from one motor lane right up to ten motor lanes!

And no, it doesn't hold traffic for long. Watch the video again. This is how long it takes for cyclists to cross in all directions on a road which has ten lanes of traffic.

It's easy to get the wrong impression from looking at blog posts and watching online videos. But luckily you don't have to only get your information that way. Come and see these road junctions in action yourself. You'll see how well they work. That is why we offer study tours (this blog exists as an adjunct to the tours, not the other way around).

Thedoc said...

Yes I stand by that because the junctions and areas in London that would benefit from this just simply don't have the space. Its all great where you have plenty of room to put a cycle track in and lots nice big footways but you cycle through the city and you are lucky if you can for a 1.2m lane in next to a 2m footway, never mind a track.

Am not saying the design sucks. Far from it. I like it but it is site specific when it comes to many areas in downtown London. Just the nature of the space needed means it's site specific alone.

I don't think you will see a design anytime soon where a zebra comes straight after a signalised crossing either. Don't see why not but the powers that be don't like it.

Also stick 100 peds per crossing cycle onto all arms and there is very quickly potential for conflict unless you expect to cyclists to wait in the junction as the cars set off. Again you would need storage space for them.

Regarding green times I misread that the peds would have their own phase somewhere in there. This does then trigger the other side of the coin which saying it only works on all red phase for traffic. Something that London traffic engineers try to eliminate as much as they can. Not because they want to but because they cannot increase capacity on the network. Again this makes this site specific.

David Hembrow said...

Thedoc: What on earth makes you think that all junctions in the Netherlands have lots of space ? They don't. Several of the examples above are in very small junctions, as I pointed out in my last response.

In the Netherlands there also used to be people who thought that there was "not enough space". It was thought to be true for exactly the same reason as people in the UK now think it is true: all the space was already allocated to motor vehicles. Please take a look at some before and after photos of Dutch city centres.

There's nothing site specific about this design of traffic light junction. The problem in the UK is in peoples' heads, not in the amount of space between buildings. London has a lot of truly enormous road junctions, but this design would also fit very nicely into many of the much smaller junctions.

Thedoc said...


Sorry I am struggling from the link you sent to see any before an after photos of anywhere except where streets have been transformed to low motor vehicle use. Not sure where you were trying to point me towards but that link cannot really translate to junctions and roads on the TLRN where you are never going to reduce the traffic in a million years.

As I said before I like the design but it's not going to happen anytime soon in London. Even on a good site the DFT will not allow it as they will not allow conflicting movements with anything and that goes for cyclists as well as motor vehicles. They treat them the same.

For that reason it looks like two stage rights are here to stay for a while. Don't like them myself but at least it's an option for people who don't want to go to the middle of the road, even if it's not ideal.

David Hembrow said...

Thedoc: The "not in a million years" attitude is the real problem, not the width of your roads.

Many of the example "before" photos on this blog and elsewhere are precisely of the most busy city streets, where people could at one time see no alternative other than to continue to allow more and more motor vehicles.

Just as there is "no space for cycle paths" in the UK now, there was "no space for cycle-paths" in the Netherlands in the 1960s. This was so extreme that in many examples, early primitive cycling infrastructure (1930s) was removed in order to make more space for cars. Cars were the future. The whole world planned for cars in the period 1950-1975.

The UK has continued to plan for cars right up to this day. That is why you still have "no space for cycle-paths". However the Dutch took a different turn in the 1970s and that is why Dutch town centres appear to have more space.

It's not that the roads are wider, but that through traffic has been removed from many of the streets where it would be a "not in a million years" issue in the UK.

You can't change by staying the same. To resolve the problems caused by current policy in the UK requires a change of policy.

Rules and guidelines are actually changed quite often. I have it on good authority from more than one British planner than Simultaneous Green could be achieved in the UK already. There are ways of tweaking the design which would allow this. What's more, there are frequently trials of different types of junction. There's no reason why this can't be one of the future trials.

But keep talking about it as if it is impossible and it'll never happen.

Thedoc said...

Quite direct in your manner of responses. Sound like you think I am stuck in the dark ages and are not pro bike. Far from it. I am a progressive engineer who is very pro cyclist and is always challenging legislation but am also a realist. You talk as if we have a choice in the matter.

We are so regulated over here it's not funny. I'll keep thinking that way until the DFT lets me think otherwise.

I don't think you understand the traffic flow situation over here though or what the function of the TLRN actually is.

I'd love to put these designs in and in a lot of places in the UK it might well happen. London is not the UK though.

In London we are well aware that cars are slowly on the decline and long may that continue. We will always promote cycling and might well find the odd street we can turn into cycle streets or low motor vehicle streets.

Major London intersections though are another story and trying to turn them into the before and after photos shown on this site is going to be virtually impossible. Not because of lack of imagination or the will of people like myself but because the need and pressure for capacity is too great.

The Ranty Highwayman said...

Thedoc - it would work, but it *just* needs a bit of will.

Don't forget, when we have all round toucan stages, there is nothing (in law) to stop anyone walking or riding the diagonal.

I know people are resistant to change and I wonder if it is they are just pro-traffic or scared that something might just work and so break the status quo.

I do know how difficult it is to get change and to some extent, it is why I blog - nothing is changing any time soon in my part of London, but I hope I can offer some direct UK inspiration.

Thedoc said...

"Don't forget, when we have all round toucan stages, there is nothing (in law) to stop anyone walking or riding the diagonal."

Hello there. I liked your blog.

True we have the all round toucans although we do try to avoid all red ped or cycle phases as much as possible on London streets purely because of the impact on capacity.

That is the main problem with the simultanious greens. Capacity of the streets where we would love to put them and also the vastly higher cycle speeds we have in London compared to those abroad.

For me cycle designs are about getting everyone out on the roads in a safe manner and not just designing for the commuter. The cycle superhighways take care of that and whatever you think of them they are occupied by mainly very quick cyclists.

Imagine us having a simultanious green in the city when and a family of four try to cycle diagonally across a junction as 100 lycra wearing adrenalin fuelled speed junkies come flying at you as soon as there is a sniff of an amber light.

Its why I said this sort of thing was very site specific in my first post but then got attacked for saying so.

Will see what happens if the DTF relax there views. I would like to see a better option than the two stage right turns that are frowned upon in this blog but at the moment there isn't a great deal of options.

I quite like some of the American designs of two way cycle lanes in the centre of the road but its difficult to deal with once you get to a junction and want people to turn left. I am always playing around with ideas though and going to try to mess around a bit with the protected design you have on your blog.


David Hembrow said...

Thedoc: I'm afraid your reply is riddled with misconceptions.

For a start, you've misunderstood how much time is required for Simultaneous Green. There is no capacity problem for drivers because green phases are short. It takes barely any longer for a cyclist to cross a road diagonally than to go straight across. If you allow diagonal cycling, no second crossing and associated delay to motorists are required.

That it saves time is one of the great advantages of Simultaneous Green. Just a few seconds are enough for hundreds of cyclists to clear these crossings. Optimum use of the space is made during the time that the lights are green.

Pedestrians diagonal crossings are a completely different matter. Because pedestrians move at a more or less constant speed, they take sqr(2) (1.414) times so long to cross diagonally. You cam save a little time over having two phases, but not lots of time as is the case with cyclist Simultaneous Green.

Next, let me assure you that London cyclists are not faster than Dutch cyclists. How on earth could that be ?

We're genetically identical, but British people cycle far less and simply are not as fit on average as the Dutch. That's why British people generally cycle much more slowly.

When I visited London myself I found that even on a boris bike cycling was frustrating because of low speeds. Short cycling journeys in London take much longer than in the Netherlands.

To believe otherwise is simply to misunderstand the reality.

There are few countries on earth where sport cycling is more popular than here. Nowhere has so many long distance fast commuters.

It is absolutely normal in the Netherlands for small children riding their own bikes to use junctions at the same time as fast commuters. It happens thousands of times every day without causing any problem.

The only reason why you think "lycra clad adrenalin fuelled speed junkies" are a problem is that your infrastructure is not up to the job of dealing with cyclists at different speeds.

I hope you are not seriously considering the ludicrous idea of putting cyclists in the middle of roads. Quite apart from how unpleasant this is (surrounded by noise and fumes from both sides), it makes it impossible for cyclists to reach destinations on the sides of the road, as well as having the problem of there being no good way of designing junctions. It's a dead end.

For good solutions, don't look to the USA. They do not have the solutions which lead to true mass cycling but are one of the few countries with less cycling than the UK.

To achieve mass cycling, you should look to countries which actually have it and look at how they achieved it. The Netherlands has a cycling rate which is nearly twice that of the second place country.

What's more, the Netherlands is just a few hundred km away, not several thousand. So it is the Netherlands which should be your first port of call, not the USA.

Please don't feel that you are being "attacked" because you are not. But you've expressed an extraordinary number of misconceptions in the few posts which you have made here and you've stated unfounded opinion as fact. Surely you expect errors to be pointed out.

Nothing is "site specific" about good design. It works well everywhere while bad design causes problems everywhere.

Instead of guessing, you really should come on a study tour and find out for yourself. You'll see how fast many people cycle here, how skilled people are at cycling in large groups and you will be able to find out how efficiently Simultaneous Green junctions work in reality.

Thedoc said...

Ill just agree to disagree on some of this for now as its like a game of tennis but in short.

"There is no capacity problem for drivers because green phases are short."
Yes there is purely because you are having any green phase at all. The area's I am talking about do not want an all red traffic phase of any kind because it kills the capacity. All red is simply not pratical in a lot of London which is why we stagger so much.

"Next, let me assure you that London cyclists are not faster than Dutch cyclists"
I am an engineer and a cyclist who recently attended a cycle design course run by Dutch and Danish engineers. They told us this an pointed out the problems it poses for us. Also I am yet to see a video to tell me otherwise. Maybe they were lying though.

"I hope you are not seriously considering the ludicrous idea of putting cyclists in the middle of roads"
No I am not not as I said. Its too difficult at junctions and getting people back into the right place.

"The only reason why you think "lycra clad adrenalin fuelled speed junkies" are a problem is that your infrastructure is not up to the job of dealing with cyclists at different speeds"
I look forward to seeing the video of cyclists over there setting off at speeds just under a motorbike as people are crossing them.

"So it is the Netherlands which should be your first port of call, not the USA."
It is and always will be. Don't think I don't love the dutch designs because I do and am trying to adopt them as much as possible but its not that straight forward.

Nothing is "site specific" about good design.
You have to really know London to say this. Feel free to knock a design up outside Monument tube station though!

Anyway have a good weekend.

David Hembrow said...

Thedoc: Sadly, I think you simply do not understand.

"All red is not practical" - This is because you are looking at continuing with the same situation as you have and not at real change. The combination of making cycling more attractive and moving driving routes away from where the junctions are which cyclists use and you have to deal with considerably fewer cars.

i.e. The problem that you face is created by the design of your roads and you're trying to solve it without changing that design.

You asked for one, so here's a video showing cycle racers on an urban cycle-path. This is not an unusual occurrence. There's no conflict because the junction design removed the conflict. That you suffer from conflict is due to your junction designs.

You come across as very aggressive. No-one is lying, but people are offering opinions on things which they simply don't understand because they are not part of their experience.

Your "Dutch and Danish engineers" will no better understand how things are in the UK than you understand how things are in reality in the Netherlands. I've been in meetings like those that you describe and heard how people talk at cross purposes. Just as British people tend to imagine that Dutch cyclists dressed in normal clothing are "slow" based mostly on appearance, Dutch people imagine that anyone dressed in lycra is "fast" also based on their appearance. They do this because the only reason why someone would dress in that way in the Netherlands would be to take part in sport - as seen in the video linked above.

There is much lost in translation and it is precisely to prevent misunderstandings like this leading people making mistakes in infrastructure design that we offer study tours. We are the only people doing this who speak native English and who have cycled for many years in the UK as well as in the Netherlands.

We're not guessing about the other country, we actually have experience of cycling there for years. And yes, that includes experience of cycling in London as well as in other cities right across both the UK and the Netherlands.

That is why I can assure you that cyclists in London are not abnormally fast. They are in fact on average rather slower than Dutch cyclists so you do not in reality face problems which the Dutch haven't already dealt with.

If you think sprint speeds of "just under a motorbike" are impressive, how about maintaining speeds greater than many motorbikes or faster than an actual cycling race ? Some people in the Netherlands ride at speeds very much faster than you seem to imagine.

Childbacktandem said...

I am interested that you appear to feel that an all-green makes crossing major multi lane junctions safe enough. Can you comment more on these larger junctions please?
'Masking' collisions are a common problem in the UK. I mean the case where a motor vehicle hits a cyclist entering the crossing because they are masked from each other by another vehicle (especially likely if it is large such as a van or lorry) in an adjacent lane.
Of course on a properly designed junction, motorists should be expecting cyclists and I can see that the diagonal path of cyclists in a simultaneous green junction will tend to draw them a little further away from vehicles which might hit them, however, these large junctions still look inherently risky.
They will tend to have high vehicle speeds (legal or not) and high motor traffic volumes leading to high exposure risks. Both cyclists and motor vehicles sometimes 'chance it' and accelerate across on amber/red.
Do you have a view on this including the appropriate motor vehicle speed limits and on how effectively they are enforced, including at off-peak times when it is easy to go fast?

David Hembrow said...

Childbacktandem: Simultaneous Green junctions aren't merely "safe enough", they're just about the safest design of large junction possible. This is because ALL motor vehicles are at a standstill behind a red traffic light when cyclists use the junction. Therefore there is no risk whatsoever. No chance for "masking" or any other effect. This is why there have been almost no injuries on simultaneous green junctions at all, ever. The only way in which injuries can occur is if drivers, cyclists or pedestrians proceed through red lights or if cyclists collide with each other.

Childbacktandem said...

Lots of people do go through red lights (drivers as well as cyclists) and in the UK pedestrians are permitted to. Under any system, collisions are almost always a result of at least one party being careless or breaking the rules.

The more motor vehicles, the faster the speeds and the more complex the junction, the longer the cycle times and the bigger the temptation. (This is not a case for changing from simultaneous green to a different design of at-grade crossing -it's trying to explore the limits for at-grade crossings).

David Hembrow said...

Childbacktandem: Some people go through red lights, but they're a minority. Collisions are the result not only of people being careless but also of infrastructure which is designed in a way which results in careless behaviour quickly leading to dangerous situations.

The simultaneous green design solves these problems to a greater degree than other traffic light junction designs because it seeks to completely isolate different modes in time as well as in space. It reduces the temptation to go through red because both cyclists and drivers have shorter waits behind red lights with simultaneous green than they do with other traffic light junction designs.

Conflicts have been entirely eliminated for those who obey the rules, temptation for those who don't obey rules is reduced and the chance of dangerous things occurring if you break the rules is also reduced because the design results in good sight-lines.

This is why the safety record - the actual result - is extremely good for simultaneous green traffic lights. There are very good arguments for other designs of traffic light crossing to be changed to simultaneous green, but not very good arguments for change from simultaneous green to other designs.

Unknown said...


I'm looking into Simultaneous Greens as I'm convinced that they are the cheapest, simplest and safest design available. Do you know whether anything has changed since you wrote this blog that makes it any more likely that their use is permitted within the UK?

David Hembrow said...

Unknown: I'm afraid I've not been following what's going on in the UK so I can't tell you whether it's more likely that Simultaneous Green is allowed now. Probably not, I would guess, as no-one seemed to be fighting for the changes which be required to make it possible. There is another design called CYCLOPS which has been built a couple of times in the UK and I think the designers have put quite a bit of effort into this with the intention of finding something with some of the advantages of Simultaneous Green which could be built in the UK. It appears to me to be a bit clunky by comparison but it may be as good as you're going to get, at least for now.

Unknown said...

Thanks for the reply David- I'm not convinced that Cyclops works in areas with high pedestrian footfall. They seem like an expensive, over-engineered solution.

David Hembrow said...

Unknown: agreed, though I hope we're both wrong. One of the problems with expensive solutions is that the expense becomes an extra reason for them to be difficult to get built. It seems that there are only a handful of cyclops junctions at the moment so they're still very experimental and later ones may be improved and simplified.
Of course the UK has suffered for decades from the problem of good interventions being few, far apart and slow to build, while road reconstruction to accommodate ever more cars is common, everywhere and quick to build. Until good things are happening more quickly than the bad there's not really any forward progress and we have to hope that that will change.