Friday 23 May 2014

The best roundabout design for cyclists. The safest Dutch design described and an explanation of why this is the most suitable for adoption elsewhere

Roundabouts are often disliked by cyclists because using them by bicycle can be fraught with danger. When riding on a roundabout, you rely upon drivers seeing you on your bike. There is a tendency for motorists to look right through cyclists while looking for other motor vehicles, hence the frequency of "SMIDSY" incidents. However none of this has to be the case. The best Dutch roundabout designs do not cause significant danger for cyclists. But note that not all Dutch roundabouts are created equal. There are big differences in the safety of different designs of roundabout used in the Netherlands, and not all advice from this country emphasizes the safest design.
This blog post is mainly about this roundabout. It's an urban roundabout used by a large volume of traffic including pedestrians, cyclists, cars. buses and trucks. It's interesting because of its very good safety record - just four crashes in five years, all minor car-car crashes, none of which involved a pedestrian or cyclist and none of which caused an injury to anyone.
There is a common misconception held in other countries that Dutch roundabouts are safe for cycling due to their geometry, but actually the roundabouts of Assen, just as other Dutch cities, vary enormously in design. The geometry of Dutch roundabouts is not the common factor which makes them safe. What makes them safe is removing cyclists from harm's way and the safety of different Dutch designs comes down very much to how well they keep cyclists away from potential injury.

In the Netherlands it is not expected that cyclists should be mixed with motorized traffic on roundabouts. There is always a cycle-path or lane of some form. While cycle-lanes around roundabouts are not generally thought to work well. there are two opposing views on how these cycle-paths should be designed. One view holds that cyclists should have priority across each road leading to the roundabout, the other holds that it is dangerous for cyclists to have this priority. The current recommendation1 is for roundabouts within towns to be the "cyclists priority" design while roundabouts outside towns give priority to motor vehicles, and many towns in the Netherlands have adopted these recommendations. However, not all towns have done this and Assen is one of the hold-outs.

Adverse camber on the roundabout
itself encourages slow speeds, which
improves safety for all users. Longer
vehicles have to use the red surfaced
raised area which further increases
the camber.
The roundabouts in Assen have a particularly good safety record even by comparison with other Dutch roundabouts in other Dutch cities. During the five year period between 2007 and 2012, there were just two cyclist injuries at all the 21 roundabouts combined. The impressive safety of Assen's roundabouts is in part due to the city having ignored the recommendations made in the CROW manual and having retained motorist priority on each of the crossings. This may sound as if it makes cycling less convenient, but we have not found this to be a significant problem. It's rare that a cyclist must put their foot down and stop. It is more often the case that cyclists adjust their speed and merge through any traffic which is crossing the roundabout. That is actually much the same as a cyclist would do on approach to any other roundabout design. In reality you must give way at some point or another on entering any design of roundabout. All that changes between these two designs is at which point you must give way.

The design of Assen's roundabouts results in crossings of roads always being at 90 degrees and the 90 degree crossing point being where cyclists must give way. This makes it easier for both drivers and cyclists to see what is happening in all directions of interest. This roundabout design also makes sight-lines longer which gives more time to react, more time to adjust speed so that it's almost always possible to cross without stopping. Both of these result in safety advantages over the other Dutch roundabout design which has an annular ring.

With this design, a significantly higher degree of safety is achieved in exchange for perhaps a very slight decrease in convenience. But the decrease in convenience is really not large as people often fear, especially when we take into account that cyclists can cross safely in both directions around roundabouts where the crossings are at 90 degrees. This saves time because it's possible to take a short-cut across the junction and reduces exposure to risk as we need cross only one arm of the roundabout to make a left turn instead of more if we had to ride all the way around the roundabout to make a left turn.

Please do watch the video as it demonstrates clearly how efficient and safe this design is. Note how at the start of the video it is demonstrated that it is possible to travel across this roundabout by bicycle without adjusting one's speed at all. This would not be the case with a "cyclist priority" roundabout or by cycling on road as in both cases a reduction of speed would have been necessary at the point of reaching the roundabout.

The video shows one of the busiest roundabouts for cyclists in Assen and demonstrates why it is both safe and convenient for cycling. Only four collisions of any type were recorded here in five years, and they were all of the "fender bender" variety, where one driver shunted another at low speed on the way on or off of the roundabout. No cyclists or pedestrians were involved in any way in any of these minor collisions and there were no injuries to the drivers either:

This is even more important for other nations
This photo has featured on many blogs
but they unfortunately picked a bad
example. This is the annular ring design
with cycle priority at the crossings
which is seven times more dangerous
than the design which I recommend.
This type of roundabouts causes between
 52 and 73 extra injuries per year in the
Netherlands. Copy the safe design
which is illustrated elsewhere in
this blog post.
It has been known within the Netherlands for many years that roundabouts which have annular ring cycle-paths and on which cyclists have priority over each arm are less safe than those of the design which we have in Assen (nationally, SWOV originally estimated an extra "52-73 in-patients a year" due to the dangerous design, there are now three times as many of them so it believed that an additional 100 to 150 cyclists a year are now hospitalized because of the poor "priority" design). The decision to favour the cycle priority design was taken in an attempt to increase cycling convenience at the cost of safety.

The safety cost of choosing cycle priority will almost certainly be greater in other nations than it is here in the Netherlands. Dutch drivers are more familiar with bicycles than drivers of other nations and there is also a good chance here that bicycles will dominate any particular roundabout, making them difficult to ignore or overlook. Neither of these factors can be relied upon in other countries. For that reason I suggest that the safer design presented here should be the only roundabout design for cyclists adopted by other nations.

2018 update: The number of roundabouts in the Netherlands has doubled since the report was written. Because the dangerous priority design was widely adopted there are now 100-150 injuries requiring in-patient treatment at hospital and concerns about the rising number of casualties due to this dangerous design. Please read more about this in a new blog post about this subject. The priority design has proven not to be beneficial to cyclists in this country and it won't be beneficial in your country either.

How much safer is this roundabout design ?
Section from the English language summary of the report on
roundabout safety. The with-priority design is barely safer
than an un-signalled crossing while the safe design shown
recommended here is very much safer.
People keep asking me how much safer this roundabout design is than the "priority" design and if there are any figures to prove this. The document linked two paragraphs ago (there's an English language summary on page 5) gives the answer quite clearly. The annular ring design with cyclist priority is 11% safer for cyclists than an un-signalled junction while the same annular ring design without cyclist priority is 87% safer for cyclists. i.e. The expected injury rate due to cyclist priority alone, on the annular ring design, is nearly seven times higher with cyclist priority ( (1-0.11) / (1-0.87) ~= 6.85).

The roundabout design recommended here is, at the very least, seven times safer than the alternative Dutch design

However the design which I recommend is specifically designed in order to improve sight lines and also to lower both cyclist and driver speeds at the point of conflict (rather than slowing cyclists only at the point of joining the ring). We can therefore reasonably expect that this design will be associated with better injury rates. Combining both the improved sight lines and the better result for priority should result in a much better than 7x improvement in safety. The difference in outcomes suggests that estimating that the improved layout results in at least a 2 or 3 times safety improvement is quite conservative, leading to the safe design described above being at least 20 times safer than the unsafe design with cyclist priority.

There is no need to guess as we do have figures. We see a very obvious result in real life statistics for roundabouts. Injuries are rare at the design which I recommend, while they are remarkably common where the annular ring design is combined with priority for cyclists. Remember that these figures come from real injury statistics in the Netherlands, with Dutch drivers who are familiar with cyclists. There is likely to be a much greater difference in safety should the same designs be tried in other countries where drivers are less familiar with and less respectful of cyclists.

Note that the 11% improvement in safety for the priority roundabout design over an un-signalled junction for Dutch cyclists with Dutch drivers is a very small figure. You shouldn't necessarily expect this to apply for cyclists in other countries from the same design. It may even be that the situation is worse than an un-signalled junction in other countries. But the very strong result from the safe roundabout design is likely to still have some significance in other countries.

Safe vs. "convenient" ?
The comparison between these two roundabout designs has in some places taken the form of an argument about safety vs. convenience. There is an attempt to paint the added convenience of one type of roundabout as a certainty while the safety advantage of the other is played down as being "very slight". In fact, it is proven that the safer design (as recommended in this blog post) is seven times safer for cyclists than the other design, while the relative convenience of the designs is open to debate. I find that the safer design is also very convenient. If you doubt this, please watch the first 80 seconds of a video in which I demonstrate how I regularly cross the roundabout illustrated above in both directions without stopping.

While the design on the left is often referred to as a "cyclist priority" roundabout, cyclists actually have to give way on both types of roundabout. The main difference is that the point where you give way is not coincident with the point of conflict on the design on the left while it is coincident with the design on the right. This means that the cyclists at most have to slow down and speed back up once with the design on the right and can do so while assuring their own safety. Note that drivers have to give way at the same point on both roundabouts, and that giving way to cyclists in the Netherlands is significant because there are often more cyclists than drivers using junctions in this country. The case shown above is a best case so far as the "priority" roundabout is concerned. Sometimes they are very much less convenient as can be seen in a video.
A much smaller example following the
safe design princples. A busy
roundabout serving a high-rise car
park which does not injure cyclists.
The principles of design are important, not this exact size and design
I chose this particular example for the video because it's very clear what is going on. It's large and it's relatively green for an urban location, but this makes makes it easy to demonstrate in a video how the roundabout works. The principles which make it safe (90 degree crossings, good sight lines, plenty of time to make decisions, obvious priority, some journeys made without joining the roundabout at all) can be, and often are, applied on a smaller scale.

The small size of the island at this
roundabout can be seen in this photo
from a recent study tour.
The smaller example illustrated here applies all the same principles as the main example above but on a much smaller scale. It could in fact be made smaller yet. There have been no cyclists or pedestrians involved in a crash here. Only two minor fender-benders between motorists are recorded, neither causing an injury.

Summary of points which make the safe roundabout safe
  1. 90 degree crossings between cyclists and drivers to improve sight-lines of both.
  2. Not relying upon drivers to take decisions which maintain the safety of cyclists or give way on behalf of cyclists but giving that control to cyclists themselves.
  3. Adverse camber for cars going around the roundabout to slow cars down.
  4. Refuges between streams of motor traffic which are wide enough to accommodate a whole bicycle.
  5. Bidirectional cycle-paths because they allow cyclists to cross fewer streams of traffic - crossings are where the dangerous interactions occur.
  6. Right turns take place with no interaction at all between cyclists and motor vehicles.
  7. The layout makes it very obvious to everyone what they should do.
Not every junction should be a roundabout
CROW suggest that roundabouts are appropriate only on junctions with up to 500-1500 motor vehicles per hour on the busiest arm of the roundabout. Note that that is a peak not an average. It doesn't imply safety with 12000-36000 motor vehicles per day, but that the peak hour should be 500-1500 max. Most roundabouts in the Netherlands have flows considerably lower than the maximum allowed. Where more vehicles must be catered for, they suggest not having cyclists going around roundabouts at all, but using other junction types such as traffic light junctions or cycle unfriendly multi-lane roundabouts which then require grade separation (see next section).

Too little space ? Too much traffic ?
Think about Simultaneous Green, the
other really good junction design.
If you are looking to copy these principles but there is not space for a safe roundabout in your location then perhaps a roundabout is not the correct solution for you. There are other possibilities. Simultaneous Green traffic lights can work even for very small junctions, but in the Netherlands note that many traffic light junctions in small streets have been removed altogether, along with the motor traffic which they used to serve. By doing this, a safe situation can be achieved almost anywhere.

For a complete picture of all the complex junctions in Assen, see previous blog posts about every roundabout in Assen and every traffic light junction in Assen.
CROW suggest that a peak (rush hour) hourly intensive above 1500 motor vehicles always requires a tunnel, a bridge or a traffic light junction to be built instead of a roundabout. These solutions are also preferred at lower traffic levels (1200-1750 or >1000) in different situations.

Don't forget about unravelling
Another factor which leads to the safety and convenience of Assen's roundabouts is that they are largely avoided by cyclists. Bicycle routes here are unravelled from driving routes. Many of the 21 roundabouts feature only infrequently on cyclists' journeys or do not feature at all.

CROW suggest that higher traffic levels should result in cyclists being grade separated. Here's an example of just that. This roundabout on the ring-road in Assen has a perfect safety record for cyclists and probably always will have. Why ? Because there's absolutely no need at all for any cyclist to ever interact with motor vehicles on this roundabout:

This roundabout is even safer for cyclists, but it cheats by not really being a roundabout for cyclists at all. Grade separation should be the norm where cycle routes cross busy ring-roads which pose a safety risk.

Other real-life Dutch roundabout designs
Below you'll find examples of other roundabout designs used elsewhere in the Netherlands. Most of these examples have a less convincing safety record than the examples illustrated above. They're shown along with their safety records in order to demonstrate what does not work well and should not be emulated elsewhere.

Shared Space "squareabouts"
Drachten is a smaller town than Assen a few kilometres to our west.

There has been considerable international attention drawn to a Shared Space "squareabout" in that town. Much has been written about this being a safe design. However, if we ignore the hype and look at the statistics then we find a very different story:
Laweiplein Shared Space "squareabout" in Dracthen. There have been ten crashes here, injuring three cyclists and one moped rider. This single Shared Space junction is more dangerous for cyclists than all of Assen's 21 roundabouts and all of Assen's Simultaneous Green traffic light junctions added together. 
Turbo Roundabouts
Turbo-roundabout under construction
by a motorway junction south of
Assen. Absolutely no bikes near here.
There has been an unfortunate mis-understanding in the UK over turbo-roundabouts with at least one council seriously trying to implement a turbo-roundabout for cyclists.

This is a huge mistake. Turbo roundabouts are designed to maximize flow of motor vehicles. They're a good design for motorway junctions and similar places where there are many motor vehicles and absolutely no cyclists or pedestrians.

Note that Turbo roundabouts are also recognized to be dangerous for motorcyclists. Motorcycling groups have complained in the Netherlands.

Dangerous roundabout in Groningen.
See the first picture below.
Groningen, which won the Fietsstad competition in 2002, is famous for having the highest cycling modal share in the world. This is the result of policies starting in the 1970s and it is also contributed to by the extremely high student population.

Unfortunately, the city has not progressed so well since 2002 as it did in the years before it was awarded a prize. Local campaigners have been vocal about this. Groningen's infrastructure is variable in quality but problems caused by this are to some extent masked by the high level of student cycling.

One of the most dangerous roundabouts in Groningen has been featured in previous blog post. We've used it for some time on study tours as a contrast with good roundabout design. To demonstrate what not to do:
This busy Groningen roundabout is the scene of 36 incidents in five years resulting in injuries to two pedestrians, three cyclists and two moped riders. This is not good design.
All of the roundabouts within Groningen are of the annular ring design and all give priority to cyclists. Unfortunately, none of them have an especially good safety record:
A suburban roundabout, relatively low traffic but with 18 crashes including six cyclist injuries.
A few metres away, this roundabout in the same suburb is the scene of 13 crashes including two cyclist injuries
This roundabout has different geometry to the other three and better sight lines. In particular, there is a wide verge the length of a car between the roundabout and the cycle-lane. This gives a space in which drivers can stop between the road and the roundabout in a similar manner to how it is possible for them to do so in the example above from Assen. However this detail but that hasn't prevented there being 8 crashes here. One cyclist and one moped rider were injured. I write about an experience at this roundabout below.
Just outside Groningen to the South we find a roundabout more similar to the design used in Assen, with better sight lines and where motorists have priority. At this roundabout there has been just one collision between a motorbike and a bicycle which unfortunately caused an injury. The vertical grey line in the roundabout is a sculpture.
Zwolle is the current holder of the "Fietsstad" award, an occasional award presented to the Dutch city which is considered to be trying hardest to grow cycling.

Zwolle's "Bicycle Roundabout", built last year, has similar
appearance to known unsafe designs and as yet no safety
record. I'm not praising it unless it turns out to be safer than
it looks.Update: See below. Cyclists were injured here within
weeks of opening.
Zwolle achieved an amazing amount of positive press last year for an unusual "bicycle roundabout" (fietsrotonde) junction design. This unproven design was even used as part of the marketing campaign for the city's Fietsstad competition entry. The "bicycle roundabout" works as a roundabout for cyclists while for drivers it is a straight through road. The kerbs are narrow, sight lines are short and crossings are not at 90 degrees. Press releases about this junction and other sources have made claims made about its safety but in my view praise should wait until there is a proven record of safety. That is why I did not write about this junction before now. We must first wait to find out what the long term safety outcome is and until then treat the new design with caution. This is especially not something for other nations to try to emulate.

It is claimed that Zwolle drivers' familiarity with existing roundabouts will lead to the bicycle roundabout being safe. I see this as spurious as while Zwolle doesn't have many other roundabouts those that it does have actually do not have a good safety record at all by Dutch standards. There are some examples below.

Update: I've discovered that the Bicycle Roundabout in Zwolle has in fact already claimed victims. It opened at the end of August 2013, the first cyclist injury was in September and another cyclist was injured in November. Zwolle's Bicycle Roundabout has therefore claimed as many victims in three months as all twenty-one of Assen's roundabouts caused in five years. Even relative to the previous supposedly unsafe situation this doesn't seem very impressive. According to the Ongelluken Kaart, there was only one injury in this location in the five years between 2007 and 2012. Also read how the Bicycle Roundabout was advertised in advance as part of the effort to win the cycling city (fietsstad) award.

Further update: Thinking more about this, it seems that the whole idea of the "bicycle roundabout" is flawed. Compared with the unsignalled junction which existed before it was built, a normal roundabout of the type used in Zwolle might be expected to achieve a 75% reduction in injuries to motor vehicle occupants but just an 11% reduction in injuries to cyclists. However, the bicycle roundabout as built doesn't meet good guidelines even for that type of roundabout. Sight lines are very short. What's more, given that part of the reason for enhanced safety for cyclists at a normal roundabout is a result of drivers being able to make a choice not to exit the roundabout at a point where there is conflict with cyclists, and given that in this instance that choice has been removed and drivers are forced to exit in conflict with cyclists, there seems no good reason at all for anyone ever to have assumed that this design would in fact be safer. Therefore the elevated injury rate due to the bicycle roundabout should be no surprise to anyone.

Update 2018: In a reader's poll in a local newspaper, the Fietsrotonde was chosen by cyclists of Zwolle as what they believed to be the most dangerous place in the city for cycling. Perhaps more worryingly, even though it had been improved since I wrote this piece, the first roundabout featured below is still of the priority design the the council now admits that this is the most dangerous place in the city for cyclists. If Zwolle had instead converted the roundabout into the the safe design which I recommend then this would not have happened.

Zwolle Urban roundabout with priority for bikes. 15 crashes here including four cyclist injuries
Update 2018: Zwolle completely rebuilt this roundabout, but instead of choosing the safe design featured at the top of this blog post they changed to a different unsafe design so this continues as the most dangerous location in Zwolle for cyclists.
Zwolle Suburban roundabout with priority for bikes. 25 crashes here including six cyclist injuries.
Another of Zwolle's cyclist priority roundabouts. 22 crashes here including two cyclist injuries
Eindhoven is a city which we used to visit quite often as for a while we thought we might settle in that area. It's a larger city with few roundabouts. Much as we've seen elsewhere, the roundabouts which have priority for cycles have injured cyclists while those which keep cyclists well away from motor traffic have not:
Eindhoven roundabout with priority for cyclists. Ten crashes in total, four cyclist injuries
This junction resembles the design used in Assen, but it is truly enormous in scale. It gives cyclists priority. The crossings are far from corners in the cycle-paths and far from the roundabout, which itself has a much larger radius and will support higher speeds. Perhaps it is the resultant speeds of both cyclists and motorists alike at the crossings which adds danger here. Two cyclists have been injured here in five years.
On the other hand, this enormous multi-laned roundabout in Eindhoven has caused no cyclist injuries at all. Why ? Cyclists are completely grade separated from motorists. Therefore, despite the huge size of this road junction, it is both safe and convenient for cyclists to use.
This is the Floraplein in Eindhoven. A turbo-roundabout. Turbo-roundabouts are designed for maximum flow of motor vehicles and should never be built where there are cyclists, but this one was. There has been much local opposition to this roundabout including a protest video showing the problems that it causes. I featured a video of this roundabout in a blog post from 2012 in which I warned against campaigners mistakenly calling for this infrastructure for cyclists. Needless to say, between 2007 and 2012 there were multiple collisions here, several involving cyclists and one cyclist had to go hospital as a result.
Valkenswaard roundabout visited in 2006. Not a safe design.
See below for statistics.
Valkenswaard is a village outside Eindhoven which we visited on the 2006 study tour. At that time I was myself impressed by the idea of cyclists having priority on roundabouts. Of course everyone is attracted to the idea of priority, but when we find out that the statistics show this design to unsafe, resulting in people having been sent to hospital because of injuries which occurred here we should of course think twice about the value of such a design.

In 2006 our group spent some time looking at and riding around this one roundabout in particular as cyclists had priority there. That's why I've included this village in these examples.

We now know that this wasn't really a good example to take notice of as even though this is just a small village and there is little traffic here, this roundabout is the site of quite a number of cyclist injuries. Compare this photo with the new Zwolle bicycle roundabout (above). The obvious similarity is part of why I am skeptical of that new design.

A roundabout which the 2006 study tour group were somewhat enamoured by. It's in a relatively low traffic situation suburban but there have been seven incidents here including three cyclist injuries. i.e. even this single roundabout in a small village is more dangerous for cyclists than all of Assen's 21 roundabouts put together. This is because the annular ring design is more dangerous for cyclists even when traffic volumes and speeds are low.

Outside Valkenswaard, a rural roundabout without priority for bikes. Just one crash, no injuries, no involvement of cyclists.
Outside Valkenswaard, a busier roundabout without priority for bikes. No cyclists involved in crashes here.
One of the most influential pieces of research in the Netherlands which convinced many people that cyclists having priority on roundabouts was a good idea was carried out in Enschede in 1991 and appeared in a report from 1992. Unfortunately, as is admitted in the conclusion of that report, their positive result was based upon research which involved just a few hours of observation. Based on their short observations, they estimated that the change in priority would have a very small effect on safety. We've now had many years to see what really happened (these roundabouts have proven themselves to be seven times more dangerous as detailed above). This is the very same roundabout as was used for the 1992 research:
The roundabout between the Knalhutteweg and Broekheunering in Enschede used for the investigation into cyclist safety with priority on roundabouts. There were 23 collisions in five years here, two of which injured cyclists, while two more injured a moped rider and a pedestrian. For cyclists, this roundabout, used so often to "prove" the safety for cyclist priority, as shown itself to be as dangerous as all 21 roundabouts in Assen combined.
A few hundred metres to the North, this is the roundabout between the Knalhutteweg and Vlierstraat. At this location, there have been 15 crashes and no fewer than five cyclists injured in five years.
Closer to the centre of the city, this roundabout has been the site of 38 crashes. In this case only one cyclist was injured, but two car occupants were also injured in one crash.
Another Enschede roundabout. This example has had 20 crashes over 5 years. Six cyclists were injured here.
Looking for relatively good examples from Enschede, I found this "roundabout", the location of just five minor crashes and no injuries over five years. Suspicious of the exposed ground on the left of the picture, I looked at Streetview which revealed that this wasn't a roundabout at all during the time when the statistics were counted. It will be interesting to see what happens here in the future. Will converting this previously very safe junction into a roundabout lead to a safety improvement ?
Fietsberaad still have the Enschede roundabout as a good example on their website. I disagree. The four roundabouts in Enschede that I feature above have wounded 14 cyclists in five years. That's seven times so many injuries as all 21 roundabouts in Assen combined. This gives each of the Enschede roundabouts which I looked at a safety record on average 36 times worse than an average roundabout in Assen.

A webcam set up to observe a roundabout in Purmerend has unfortunately led to people from the English speaking world thinking that they're observing a safe example from which to copy. In fact, the Purmerend roundabout has caused many injuries to cyclists:
The roundabout in Purmerend near the software company "Archie CRM" has caused many crashes. It is recorded that twelve crashes occurred and that those crashes injured six cyclists such that they required hospitalization in just the two years of 2008 and 2009. There's a lack of data for other years but the design of this junction has not changed.
Den Bosch is another of the cities where the more dangerous design is preferred and another where the most dangerous junctions for cyclists are roundabouts.
The most dangerous junction for cyclists in 's-Hertongenbosch is this roundabout which caused hospitalization injuries to five cyclists and three moped riders in the three years between 2008 and 2010. These are not good examples of roundabouts to copy from.
Update: Where the danger comes from
It seems I need to explain more about why the roundabouts with priority dangerous, regardless of their layout. It's not just that the annular design of cycle-paths makes visible difficult but also that it expects perfect behaviour from drivers.

Giving cyclists "priority" sounds positive, but what actually happens with the priority design of roundabout design is that cyclists are stripped of control. The design requires that cyclists should ride out in front of motor vehicles and hope for the best. On this type of junction design, cyclists are used as mobile traffic calming devices. The cyclist priority design requires that drivers who don't know the rules, are tired, talking on the telephone, changing channel on their radios, arguing with other people in their cars, who can't see out of misted windows, who are impatient and don't want to stop for a cyclist (especially important in other nations where there is more anti-cycling sentiment than here) or who are simply not skilled at driving must never make a mistake because the safety of cyclists depends almost entirely on the driver and not on the cyclist themselves.

My view is that cyclists make better decisions about their own safety than drivers can make for them. This is supported by the comparative injury statistics above for roundabouts which give cyclists control over their own safety vs. those which give them "priority" or supposedly let them share equally with drivers.

An incident from earlier this week may help to explain. Judy and I rode nearly 80 km planning a cycling holiday route and we passed seven roundabouts on our way. Five of them were of the safe design and were crossed without stopping. One was of the safe design and we had to wait about ten seconds.

I'm the red arrow, the learner is the blue
arrow, the woman from the right is the
green arrow. There's too much to look
out for here. That's the problem with
this design. Good design doesn't rely
upon bright yellow warning signs to
try to enforce priority.
Just one of the roundabouts on our route was of the "priority" design. This just happened to be the same roundabout as I had already written about above as one of the safest in Groningen (it has better sight-lines than many and there have been 'only' eight crashes). On this roundabout, we needed to go straight on (second exit) so joined the annular cycle-path. At the same time as I joined the cycle-path around the roundabout, a learner driver who had been travelling parallel with me with his right indicator flashing joined the roundabout. I had to trust that the learner had seen me, that he understood the priority rules and that he was going to stop. He did, but he did so a little late and his front bumper was uncomfortably near the cycle-lane. My attention was distracted by the learner approaching from my left and I wasn't looking out for the driver coming from my right who had also not been paying attention and who stopped her car very sharply half way across the cycle lane in front of me. I had to swerve to avoid her car.

There was no crash and both these drivers stopped, but they both did so too late. With slightly different timing, for instance if either the drivers or myself had been going slightly faster or slightly slower, it could have worked out differently. This is not fail safe design. SWOV point out that "drivers have to make (too) many observations in a brief time span, resulting in them noticing cyclists too late" and that is precisely what seems to happen at cyclist priority roundabouts.

That is but one anecdotal illustration of the type of incident which simply doesn't happen with the roundabout design which I prefer, and which has been proven to be safer. We have known for more than a hundred years that we cannot rely upon perfect behaviour from drivers but this is what the priority roundabout design does rely upon. Instead of cyclists being able to take safety into their own hands, their control is taken away and their safety is assured only by drivers behaving perfectly. The roundabout priority design flies in the face of the sustainable safety principles which otherwise keep Dutch roads safe.

Even very young cyclists can ride
safely across this junction in Assen
where cyclists have priority over
drtivers. Perfect safety record here.
This blog post is about roundabouts
Don't confuse the concerns about safety at roundabouts with priority with other locations and situations. It is never helpful to try to apply a one size solution to all problems.

Concerns about roundabout priority do not apply in other situations. There are many thousands of safely designed junctions between roads and cycle-paths, here in Assen and elsewhere in the Netherlands, where cyclists have priority. Where this is the right solution. i.e. junction design is good, sight lines are long and traffic volumes and speed are not overly high, these junctions have very good, often perfect, safety records.

It is the existence of such infrastructure which makes cycling both convenient and safe in the Netherlands.

Find out more
Book a study tour to find out more about good junction design and other factors which lead to the high rate of cycling and good safety record for cyclists in the Netherlands.

1 The CROW Design Manual for Bicycle Traffic states that "On roundabouts inside built-up areas, it is recommended that cyclists on separate paths continue to have right of way. After all, this corresponds with a cyclist-friendly policy". I disagree that this is the best way to design roundabouts, especially when considering road conditions and existing road use conventions in other nations. The CROW manual also refers to low traffic (less than 6000 pcu/day) roundabouts as not requiring cycling infrastructure. In reality, roundabouts in the Netherlands without cycling infrastructure are roughly as common as unicorns. I can't remember seeing a single example.

The Dutch Institute for Road Safety Research, SWOV, are also skeptical about roundabouts which give priority to cyclists. You can read more from them here:,

Part way through writing this blog post, several people drew my attention to the new Austroads document about cycle-lanes around roundabouts. They came to a correct conclusion that encouraging people to cycle around the edge of roundabouts is a bad idea, but their suggested fix (sharrows to encourage cyclists to "take the lane") is not adequate. The design presented above works well for all abilities of cyclist.

All the aerial photographs with flags showing collisions on this page come from the excellent ongelukken kaart. This shows all crashes in the Netherlands between 2007 and 2012. Blue flags indicates crashes and the number is how crashes have occured at that location. Yellow flagss indicate that at least one injury occured, red indicates at least one death

This post originally referred to 19 roundabouts in Assen which I had written about in a previous blog post. That has now been updated to cover an additional two roundabouts which I overlooked. These had also not injured cyclists.

Update 2018: A study tour participant made this drone video of the roundabout at the top of the article:

Friday 16 May 2014

A temporary signalled crossing for cyclists (Road works vs. the Dutch cyclist)

Where cycling is at a high level, chances can't be taken with what would happen if cyclists were redirected from safe and direct cycle-paths onto busy unpleasant roads. The result could be a catastrophic change in how people travel.

Cycling is very fragile.

If people have unpleasant experiences when cycling, they are likely to give up and make their future journeys by a different mode. This is why a comprehensive grid of very high quality infrastructure which keeps cyclists away from cars is essential to achieve the cycling potential of any area given local demographics and geography. It's also why in the absence of safe cycling infrastructure, no amount of training results in people cycling more.

The details are important. This temporary traffic island makes it possible for people to stop in the middle of the road in safety. In the video, a teenage boy starts to cross the road against a red light and benefits from this island. Note that just as at permanent crossings, cyclists are not required to stop in the middle and wait for another light. Crossing the road is always achieved in one motion.

Though this is a temporary cycle-path, the give way line is marked in an obvious way and there is a very flat transition between the road and the cycle-path. In fact, this temporary cycle-path is smoother than the service road to which it connects.

The signs, markings and signals are all familiar to anyone who is used to Dutch cycling infrastructure. There is nothing new to learn, no surprises due to anything operating in an unusual way. This consistency leads to safety.

In this instance it was not possible to construct a temporary crossing right next to the old crossing. Therefore the redirection signs had to be clear and obvious. This sign design is standard for redirections during road-works.
This is not an example of something exceptional, but of the norm. In the Netherlands it is normal that cyclists' routes are maintained when cycle-paths have to be dug up. Please read the many other examples of road works vs. the Dutch cyclist going back six years on this blog or see other examples of maintenance.

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.