New kent " Turbo Roundabout" with "colour coded" routes

[Greg07]

According to local press, Kent on line [https://www.kentonline.co.uk/maidstone/ ... ut-303862/]
I can't wait for Auto Shenanigans to "do" this one !
Do they mean the actual road surface is coloured ? Has this been done anywhere before ?

[BurningHorizons]

Simister Island (M62/M60/M66) has colour coded "routes".

[Ben302]

I'd take anything to improve the shocking lane discipline by users of the roundabout. As a daily user I regularly make one of two movements. A229 South to M20 Londonbound and M20 Londonbound to A229 North. The Latter is usually a straightforward left turn. The first movement is less so as the roundabout gains a lane under the A229 so you end up with lane 1 which is for aylesford and M20 and lane 2 which is marked M20 Lon Ash a229. This means it handles alot of movements and if some one in lane 1 deides they want to head for any northbound direction they conflict with traffic trying to exit onto the M20 and regular collisions happen usually on this (the busier) side of the roundabout. Will be interesting what the final design will be. the other issue is people in lane 1 approaching from the North and wanting to use the M20 will often queue jump and drive around the outside of the roundabout. Reading the comments on the article paints this as a major issue that will only be resolved by camera enforcement.

[Gareth Thomas]

I can't wait for Auto Shenanigans to "do" this one !

Jon would have quite a bit to say, I suspect.

*grabs snacks*

[nowster]

Simister Island (M62/M60/M66) has colour coded "routes".

I think they've faded now.

[B1040]

Two issues in my mind.
Folk need to know which lane to be in fairly early on (especially if they're unfamiliar with the junction). Destinations painted on the road can be hard to read if there's a traffic jam on them, and they fade.
I would say the signs at the M42 / M40 diverge at Solihull westbound are a bit late.
Then there are the deliberate lane jumpers, not much you can do about them.

[Peter Freeman]

I'll be very interested to see the detailed design for this. It's not a location that I'd have thought suitable for a Turbo-roundabout: I associate them with small and medium locations, physically and in traffic volume. Also, this rbt shows acute congestion only at peaks on the southbound approach, and it hasn't even been signalised or flared yet. It wouldn't be on my radar for this degree of upgrade, but bring it on and let's see.

A characteristic of signalised non-rotary intersections is that they can be designed, and signed, to enable you to select a lane as you approach and simply stay in it until it leads you out safely and easily onto your desired continuation. It's why they work so well. The design objective for a Turbo is to emulate this property. Vehicles enter the roundabout into a lane that will lead them naturally to their desired exit, without changing lanes while circulating or exiting. They are an extreme extension of spirally-marked rbts, which UK already uses. Spirally-marked rbts, when stacked like M60J18, have a cousin relationship with 3-level diamonds.

A fully-developed and fully-complying large-scale implementation would look something like this -
https://www.bing.com/images/search?view ... ajaxserp=0
Practical examples tend to have compromises, such as fewer entry lanes, some merging, diverging, and more signals, in order to save cost and space.

[Bryn666]

I too have doubts given that DMRB has no allowances for turbo roundabout design, and I fear that this will just be an awkwardly marked out and poorly signed attempt that undermines the design objective.

[Peter Freeman]

I think it might just be spiralled.

[Vierwielen]

I too have doubts given that DMRB has no allowances for turbo roundabout design, and I fear that this will just be an awkwardly marked out and poorly signed attempt that undermines the design objective.

The advance signs will need to identify the exits as the "red exit", "blue exit", "yellow exit" etc. WHat is also a concern is that it appears that coloured tarmac on a road is less hard-wearing than ordinary black tarmac!

[jnty]

This sounds a bit gimmicky - the colour will probably wear out quickly, won't be obvious in the dark or wet and will be of limited use to colourblind drivers. If you wanted to experiment with colours on roundabouts, it seems like a better option would be to alternatively mark each lane with one of two highly contrasting colours - plain tarmac and white would be ideal if you could get the two surfaces to have roughly equivalent traction.

[Peter Freeman]

... the other issue is people in lane 1 approaching from the North and wanting to use the M20 will often queue jump and drive around the outside of the roundabout. Reading the comments on the article paints this as a major issue that will only be resolved by camera enforcement.

In many cases where drivers knowingly and persistently use a disallowed lane, the best solution is to formalise it.

Here there's a long queue southbound in the right lane to this 5-arm roundabout, waiting to turn right (4th exit). Frustrated drivers, also wanting to turn right to London, bypass that queue via the left lane. This leads to an attractive, quicker, but disallowed route to the same 4th exit, using the left lane of the roundabout all the way. A solution could be to allow both of those southbound approach lanes to be legally used for that movement, marking the road accordingly. Low cost, might work.

According to G.Maps, that 500m (!) queue on the southbound approach to the southern roundabout is the only (congestion) problem that occurs at M20J6. The rest is collateral.

Have the turbo-conversion works begun now? The article said April 15.

[AnOrdinarySABREUser]

Edit: I fixed the image link. Sorry for the gigantic image though - I'm not sure how to collapse it.
I found a diagram of the scheme in the local press:
https://www.kentonline.co.uk/maidstone/ ... ks-304974/

It doesn’t seem like there’s any coloured lanes - only chevrons. The roundabout markings are interesting though, I prefer them over regular signage in the UK. Less confusing. It doesn’t seem that much capacity has been added to the junction though, I’m afraid.

[Chris5156]

It doesn’t seem like there’s any coloured lanes - only chevrons. The roundabout markings are interesting though, I prefer them over regular signage in the UK. Less confusing. It doesn’t seem that much capacity has been added to the junction though, I’m afraid.

Thanks for the link - that's interesting. It doesn't look like much of a turbo roundabout, it's more of a spiralised roundabout with more heavy-handed visual cues to encourage people to stay in lane. The new painted arrow designs look interesting though; if successful they might be a way to mark roundabout approaches for right turns.

[Bryn666]

It doesn’t seem like there’s any coloured lanes - only chevrons. The roundabout markings are interesting though, I prefer them over regular signage in the UK. Less confusing. It doesn’t seem that much capacity has been added to the junction though, I’m afraid.

Thanks for the link - that's interesting. It doesn't look like much of a turbo roundabout, it's more of a spiralised roundabout with more heavy-handed visual cues to encourage people to stay in lane. The new painted arrow designs look interesting though; if successful they might be a way to mark roundabout approaches for right turns.

I'd love to know if DfT has authorised them, and if they have it blows the nonsense in DMRB about right turn arrows being confusing right out of the airlock.

But as you have correctly identified, this is just an advanced spiral roundabout. A turbo uses physical kerbs and this seemingly doesn't, unless they propose to use flexible wands to reinforce the segregation between lanes.

[Debaser]

The last attempt at a 'true' turbo roundabout (turborotonde) was scuppered by one Lembit Opik (yes, that one), in his capacity as Director of Communications and Public Affairs for the Motorcycle Action Group. In the Netherlands they use raised dividers (somewhat similar to the old-school raised dividers used to separate footways and cycleways), which, if used in the UK, would apparently lead to carnage amongst motorcyclists - losing kneecaps left right and centre. Leading to the question is it impossible for a UK motorcyclist to navigate a roundabout without getting a full lean on and imagining they're going through the Luffield corner at Silverstone?

I do like the proposed chevrons separating streams though. There's usually a huge amount of wasted space on the circulatory of a roundabout due to the need to accommodate the swept paths of multiple adjacent HGVs circulating the same point at the same time.

[Bryn666]

The last attempt at a 'true' turbo roundabout (turborotonde) was scuppered by one Lembit Opik (yes, that one), in his capacity as Director of Communications and Public Affairs for the Motorcycle Action Group. In the Netherlands they use raised dividers (somewhat similar to the old-school raised dividers used to separate footways and cycleways), which, if used in the UK, would apparently lead to carnage amongst motorcyclists - losing kneecaps left right and centre. Leading to the question is it impossible for a UK motorcyclist to navigate a roundabout without getting a full lean on and imagining they're going through the Luffield corner at Silverstone?

I do like the proposed chevrons separating streams though. There's usually a huge amount of wasted space on the circulatory of a roundabout due to the need to accommodate the swept paths of multiple adjacent HGVs circulating the same point at the same time.

"Brrrm brrm go fast" is a hell of a drug in this country.

[Peter Freeman]

Unexpectedly, I like the proposed road painting. In capacity terms, and for solving the congestion problem, it might not be quite sufficient, but it's a good try so let's see.

It does allow both southbound entry lanes to be used to turn right to London - that's the main capacity issue. And that also addresses the queue-jumping and lane-abuse issue.

The diagrams painted on the road, showing small-scale plans of the circulatory carriageway, are clever; and, I hope, self-explanatory. They'll need to be well-maintained, and I hope there will be equivalent vertical, pole-mounted signage (gantries are too much to expect). The spiralisation is nicely shaped. I love roundabout spiralisation. I'd call this one half-way to a turbo.

I look forward to hearing (from Ben302?) how well it works.

[tom66]

I do like the roundabout-style arrow indications on the road. I think those are much better than the current arrangement of "left for left, ahead for just about anything else". They seem quite common in Europe and I don't think they're particularly confusing. Saw them in the US too on the odd roundabout.

[Bryn666]

I do like the roundabout-style arrow indications on the road. I think those are much better than the current arrangement of "left for left, ahead for just about anything else". They seem quite common in Europe and I don't think they're particularly confusing. Saw them in the US too on the odd roundabout.

I agree, pity the DfT doesn't. I've not seen an authorisation for them yet either which could be difficult for the highway authority if someone cocks up the basic task of following road markings.

We are so stuck in our ways in this country and there are supposed "policy experts" that know very little but seem to think exceptionalism is equivalent to being good. This is why we don't have signs the rest of Europe copes with, we still use weird excuses for not using turn arrows and segregation of vehicles, and why our roundabouts are usually complete disasters.