CTC capitulation?

[Pete Owens]

And all roundabouts are crap. FACT.

All UK roundabouts are indeed crap - which is why dealing with them by schemes such as this is such a worthwhile exercise.

 

[dellzeqq]

It's about position as well as speed- placing turning vehicles at right angles to circulating traffic to minimise the risk of cyclists being in blindspots.

as in traffic lights?

 

[dellzeqq]

All UK roundabouts are indeed crap - which is why dealing with them by schemes such as this is such a worthwhile exercise.

every roundabout I've ever seen in any country, including Holland has been crap. But for reasons you're going to have to work out for yourself.

 

[jonesy]

as in traffic lights?

Conflicts between turning vehicles and cyclists also occur at signalised junctions.

 

[Wobblers]

1. Drivers: Its bleedin obvious to anyone who has ever driven a car that you need to slow down for bends - and the tighter the bend the more you need to slow down.
2. Dutch Highway Engineers: The empirical research the Dutch did after they converted the first 100 or so roundabouts. The idea was to improve safety by reducing speeds - speeds did reduce resulting in a 70% reduction in crashes - so they rolled it out to convert all 2-lane roundabouts.
3. 'O' level physics - The coefficient of friction of rubber on tarmac limits the speed you can drive round a bend without skidding.

Its not a matter of getting used to it it is a matter of physical limitations.

No. This is a first.

Points 1, 2, 4 are valid - but it is hard to see how any safety scheme in the UK would address this (other than requiring Dutch citizenship as a condition of holding a UK driving licence).
Point 3 is not the case - all the evidence points to cycle tracks increasing the danger at junctions.

And the argument is not just that Dutch roundabouts perform better than UK ones (precisely because they are designed to restrict speeds while ours are intended to maximise them) It is that applying turbo geometry vastly improved the safety of what were already relatively safe roundabouts - they already had all the features you list before they were converted - and already had some of the geometrical features such as perpendicular approaches and exits. If they can reduce crashes on Dutch roundabouts by 70% we can expect an even greater improvement by converting UK ones.

Perhaps when you provide some supporting your opinion.


OK here is a tutorial from a numerate biker explaining how tight bends limit vehicle speed:
http://www.stevemunden.com/leanangle.html

There are a few unspoken assumptions here. You're assuming that motorists are rational, and thus will behave in a rational way (slow down!) when confronted by this new model of roundabout. The fact that fatalities in rural roads are considerably higher than motorways which have faster speeds and higher traffic volumes casts some doubt onto this assumption.

You are assuming that slower vehicles automatically means a safer environment for cyclists. While this at first glance seems reasonable you do not consider any confounding factors. Are sight lines better or worse than conventional roundabouts? If the design means that cyclists are less likely to be seen, this would make it considerably less safe. Furthermore, sharper turns mean that large vehicles are much more likely to intrude into spaces that vulnerable users may consider safe - the side of the road, or pavements. I have to point out that the majority of cyclists killed in London in recent years have been due collisions with large vehicles. Does this design make this type of incident more likely?

You claim that this sort of feature will improve safety for vulnerable users. Yes, I think that this is not at all unreasonable - but this is still a supposition. You have failed to provide any supporting evidence. No, saying that crashes have been reduced by 70% according to Dutch traffic engineers doesn't count. I need to see the source of that. Most importantly, you have failed to supply the confidence figures for that 70%. Without that, it is entirely impossible to make any assessment as to the validity of that data. (And I also note that you say "crashes", not "cyclist casualties" - does this figure include all traffic? If it does, it is meaningless from the aspect of vulnerable user safety.)

As a physicist, when I publish something, I am obliged to support it with all data, and demonstrate that my conclusions are supported by the data. My work has no safety implications - this does. As such, I don't think it unfair to ask you to provide supporting evidence to the same standards as are required in science publications.

 

[Pete Owens]

As a physicist, when I publish something, I am obliged to support it with all data, and demonstrate that my conclusions are supported by the data. My work has no safety implications - this does. As such, I don't think it unfair to ask you to provide supporting evidence to the same standards as are required in science publications.

Well, you managed to "publish" those 4 paragraphs with no supporting evidence at all! - but I suppose you also refrained from actually making any point whatsoever - just giving the impression of doubt.

It is not an "assumption" that drivers need to slow down for tight bends - it is a physical limitation. Perhaps as a physicist you could take the trouble yourself to do the maths to calculate the maximum possible speed that a vehicle can follow a 15m radius bend with only the friction of the tyres to provide the necessary centripetal force - allow say a coefficient of friction of 0.65 for a rolling tyre on tarmac. I did supply a helpful link if you cant remember the basics:
http://www.stevemunden.com/leanangle.html

Are you seriously doubting that lower speeds make for a safer environment? or just making a silly debating point?
Perhaps this might help:
https://www.swov.nl/rapport/Factsheets/UK/FS_Speed.pdf

Now for sightlines. The perpendicular arms mean that drivers nearing the junction will have a better view of circulating traffic than with the standard UK tangential arms. So drivers are more likely to cyclists, thus making the junction safer.

Lane dividers are provided to ensure vehicles keep to the lanes and trucks will need to occupy the whole lane. The lanes won't be wide enough for cyclists to overtake on the wrong side or for left turning trucks to attempt to overtake cyclists - and there won't be cycle lanes to encourage conflicting movements through the junction or traffic lights to generate stationary traffic, so this should greatly reduce the left hook problem.

 

[jonesy]

It would help take this discussion forwards if people read the documents on roundabouts and continental geometry that have already been posted. It really is not controversial to assert that people drive more slowly round a corner if the turning radius is reduced.

 

[GrumpyGregry]

It would help take this discussion forwards if people read the documents on roundabouts and continental geometry that have already been posted. It really is not controversial to assert that people drive more slowly round a corner if the turning radius is reduced.

To what degree must the turning radius on a roundabout, junction, or corner/bend, be reduced in order to ensure a motor vehicle must reduce its speed to below 20mph to 'make' the turn? 15mph? 10mph? 5mph?

 

[benb]

Most importantly, you have failed to supply the confidence figures for that 70%. Without that, it is entirely impossible to make any assessment as to the validity of that data. (And I also note that you say "crashes", not "cyclist casualties" - does this figure include all traffic? If it does, it is meaningless from the aspect of vulnerable user safety.)

Well seeing as in the Netherlands they specifically route cycling traffic away from these turbo roundabouts, because they are actually quite dangerous for cyclists, so there's your answer.

 

[jonesy]

Well seeing as in the Netherlands they specifically route cycling traffic away from these turbo roundabouts, because they are actually quite dangerous for cyclists, so there's your answer.

Er no. That's your interpretation. Apart from anything else you are forgetting that the Dutch are adding these to existing roads where the cycle networks already exist and already involve extensive segregation. You are also forgetting that the Dutch approach to roundabout design is quite different from the UK, so you can't assume that applying a turbo design to replace a UK roundabout will be worse for cyclists. Any chance of anyone bothering to read the reports posted earlier?

 

[oldstrath]

It would help take this discussion forwards if people read the documents on roundabouts and continental geometry that have already been posted. It really is not controversial to assert that people drive more slowly round a corner if the turning radius is reduced.

My problem with a lot of this is the assumption that the lane division will produce predictable behaviours and reduce speeds. If these lanes were, in fact, physically separated this would clearly be the case. But they will be separated only by small plastic 'bumps' apparently, and I (and probably others) have no faith that hurrying, late, or confused motorists won't simply ignore the lanes. In short, believing that this will aid cyclist safety requires believing that motorists will drive considerately, carefully, and in accordance with the rules of this piece of road. Given that according to the AA over half of motorists imagine that bikes sometimes 'come out of nowhere (http://www.cyclingweekly.co.uk/news...groups-welcome-aas-think-bike-campaign-116946) I think relying on their intelligence, courtesy or eyesight may be optimistic.

 

[Flying Dodo]

What of course is needed is a method of changing direction on a bike at busy major and relatively minor 4 or 5 way junctions that does not slow you down much while at the same time not bringing you into any sort of conflict with a vehicle.
It is called a roundabout. Netherlands style, never felt safer. To have priority and respect from motor vehicles is quite something. I don't particularly care if it takes away your "right" to mix it with traffic, cyclists are getting injured and sometimes dying on UK roundabouts, the solution does not include faffing around with compromises and half measures as is this governments wont.
Either go the whole hog or don't bother, everywhere.

The big problem is that in the Netherlands, most motorists are also cyclists, and so the whole culture is different. Cyclists are respected, not treated with contempt as they generally are here in the UK. So it's not a change in infrastructure that's required, but a complete change in attitude. And that's the complicated bit.

 

[stowie]

Er no. That's your interpretation. Apart from anything else you are forgetting that the Dutch are adding these to existing roads where the cycle networks already exist and already involve extensive segregation. You are also forgetting that the Dutch approach to roundabout design is quite different from the UK, so you can't assume that applying a turbo design to replace a UK roundabout will be worse for cyclists. Any chance of anyone bothering to read the reports posted earlier?

The issue I have is that the reports - from what I can see - do not take data from existing turbo roundabouts on traffic speed and use this to inform whether the 10-15mph speeds are attainable. Looking at the coefficient of friction is lovely, but I am really doubting that the highway engineers are going to make a busy roundabout where the speed limitation is 15mph before drivers start feeling their car sliding. The speed reduction is critical to aiding cyclists. The turbo roundabout is supposed to at least maintain, if not increase, traffic flow through it, and if speed is reduced, the only way to do this is increase traffic density. Which is what a turbo roundabout does by segregating the lanes and allowing vehicles to use all the space instead of having vehicles on the roundabout use the lanes to maintain speed. If the speed is only reduced to 25mph (which is still slower than now) then I would be concerned that the traffic density and speed would be such that a cyclist would find negotiating space challenging.

Then there is the fact that the lanes will be wide enough for HGVs which means that, by the councils own admission, the lanes may be wide enough for cars to overtake cyclists in them. This sounds very uncomfortable and we are back to relying on cyclists taking primary (and stick from impatient drivers) to maintain space.

Finally, the divisions are plastic and can be driven over. It doesn't take a hugely cynical attitude to think that, once drivers have got used to the design they may maintain speed by driving over the divisions. This depends on how big the divisions are. Again Netherlands drivers aren't a special breed, they will be impatient at times and look for a short cut - how does Holland maintain segregation, how easy is to go over the divisions there? Are we using the same dividers or something different?

These are simple questions. I have seen the 10-15mph repeated often, yet it is an ambitious target for vehicle use and I wonder what existing turbo roundabout speeds are like?

 

[stowie]

The big problem is that in the Netherlands, most motorists are also cyclists, and so the whole culture is different. Cyclists are respected, not treated with contempt as they generally are here in the UK. So it's not a change in infrastructure that's required, but a complete change in attitude. And that's the complicated bit.

This is true, although attitude is changing slowly - principally in London. Don't think that drivers all delight in cyclists though - I have heard colleagues in Copenhagen cursing cyclists on the roads when they have been driving, but the difference is that drivers are concerned / scared enough of hitting a cyclist to be really wary when driving.

The attitude change needs to come from the top - from politicians, local government, police and the courts. I do think that a change in attitude can be driven in tandem with a change in infrastructure. I am very open to the possibility that changing the attitudes of those in - or with - power is more urgent than infrastructure, but that doesn't excuse poorly designed schemes which use money that might be better used elsewhere (maybe put into the CTC road justice campaign for instance).

 

[totallyfixed]

The big problem is that in the Netherlands, most motorists are also cyclists, and so the whole culture is different. Cyclists are respected, not treated with contempt as they generally are here in the UK. So it's not a change in infrastructure that's required, but a complete change in attitude. And that's the complicated bit.

Yes absolutely agree, but of course it's a bit chicken and egg. What could well be true though is that if enough infrastructure is provided plus more incentive to ride then numbers ought to increase and a tipping point is reached where the majority of people ride a bike. When this happens then cyclists will have a bigger say in changing the traffic laws.
Very good friends of ours live in Nijmegen in the Netherlands, they also lived in Cambridge for several years, highly intelligent, one runs a beginners racing group for women. Their view on cycling in the UK is that we are living in the past and worship cars, all their friends are of a similar opinion. They came over to visit a couple of years ago pulling a kiddie trailer with their daughter, they said planning a safe route on the UK side was a nightmare. They are not slow cyclists, but in the city they just ride at a similar pace to everyone else, and that is a crucial difference also between people on bikes, no one is trying to "scalp" anyone else, it's all just very laid back, very refreshing.