The radii on my loops are around 100m, which is plenty. It's also only the secondary movements that use the loops - the strategic right turns (M1sb->expressway sb and M1nb->A421nb) are via semi-direct or cyclic connectors with much larger radii.6637 wrote:Hmm, I don't think that's very a good design due to the tightness of the loops. Probably better to use more land for the junction and thus have more gradual curves, like on my map.jackal wrote:I agree, it's a tough one! This is my best attempt at it. Looks ugly but does freeflow all the Oxbridge expressway<->M1 movements, plus MK<->Bedford (which currently accounts for 40% or so of turning movements here).M1 J13 large.png6637 wrote:Designing a good design for M1J13 after upgrading is tricky. Here's my attempt; I tried to make as many movements as possible freeflow.
A421.png
Note: That M1SE - A421NE turn is pretty tight, not sure if it fits or not. If not, it doesn't matter because there's another freeflow way to do this movement on the map.
Note: I've just noticed that on my map, the new-expressway-northeastbound-to-M1-southeastbound movement isn't freeflow. I should modify the map a bit, adding a freeflow link.
Oxford to Cambridge expressway
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Re: Oxford to Cambridge expressway
Re: Oxford to Cambridge expressway
100m loops are likely to be an advisory 30 mph limit which is still higher than many European loops, like in France, where the speed limit on them is just 18 mph (30 km/h).
Bryn
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Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.
Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
Re: Oxford to Cambridge expressway
With my 'realistic' engineering hat on, here's my offering. Let's face it, we would all love a fully-freeflow junction between the A421 and M1 but with the local roads, existing A421 towards MK, and the fact the current junction setup is a botched upgrade of an older junction it's hard to improve without demolishing the whole thing and starting again (which is best but prohibitively expensive).
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
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Re: Oxford to Cambridge expressway
That's a nice, neat and simple looking junction! The simpler the better in cost terms as it is cheaper to minimise the number of over bridges required as part of the grade separation.darkcape wrote:With my 'realistic' engineering hat on, here's my offering. Let's face it, we would all love a fully-freeflow junction between the A421 and M1 but with the local roads, existing A421 towards MK, and the fact the current junction setup is a botched upgrade of an older junction it's hard to improve without demolishing the whole thing and starting again (which is best but prohibitively expensive).
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
M1 J13b.png
Re: Oxford to Cambridge expressway
Similar to my more 'realistic' attempt, though I couldn't resist putting in freeflow from the M1N to the new expressway.darkcape wrote:With my 'realistic' engineering hat on, here's my offering. Let's face it, we would all love a fully-freeflow junction between the A421 and M1 but with the local roads, existing A421 towards MK, and the fact the current junction setup is a botched upgrade of an older junction it's hard to improve without demolishing the whole thing and starting again (which is best but prohibitively expensive).
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
M1 J13b.png
Last edited by jackal on Tue Nov 29, 2016 12:32, edited 1 time in total.
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Re: Oxford to Cambridge expressway
I prefer the earlier one without free flow to/from M1 to/from the expressway given long distance traffic would not really make such a movement from the east as the A14 (should be M14 in my opinion but I won't go off topic by going on about that again) is the strategic link to the M1/M6 nor from the south as the A43 is the strategic link to the M1. Realistically only local traffic would make these movements and the expense of giving local traffic free-flow should be spared. In my opinion the most important movements to give free flow to is from A421 south-westbound to M1 south-bound and M1 northbound to A421 north-eastbound. This is because the A421 (since being upgraded) now provides a link between the M1 and A1. Western M25 clockwise traffic heading for the A1 can now use the M1 to jct 13 (more direct and gets off the M25 before the northern section) and then cut across to the A1 via the A421.jackal wrote:Similar to my more 'realistic' attempt, though I couldn't resist putting in freeflow from the M1N to the new expressway.darkcape wrote:With my 'realistic' engineering hat on, here's my offering. Let's face it, we would all love a fully-freeflow junction between the A421 and M1 but with the local roads, existing A421 towards MK, and the fact the current junction setup is a botched upgrade of an older junction it's hard to improve without demolishing the whole thing and starting again (which is best but prohibitively expensive).
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
M1 J13b.png
M1 J13.PNG
Re: Oxford to Cambridge expressway
The M1N<->expressway movements are for traffic between the East Midlands and the South (e.g. Oxford, Southampton and the M4 corridor). These are strategically important, and the A14 is no help with them - it doesn't go in the right direction at all.Philip_Baum wrote:I prefer the earlier one without free flow to/from M1 to/from the expressway given long distance traffic would not really make such a movement from the east as the A14 (should be M14 in my opinion) is the strategic link to the M1/M6 nor from the south as the A43 is the strategic link to the M1. Realistically only local traffic would make these movements and the expense of giving local traffic free-flow should be spared. In my opinion the most important movements to give free flow to is from A421 south-westbound to M1 south-bound and M1 northbound to A421 north-eastbound. This is because the A421 (since being upgraded) now provides a link between the M1 and A1. Western M25 clockwise traffic heading for the A1 can now use the M1 to jct 13 (more direct and gets off the M25 before the northern section) and then cut across to the A1 via the A421.jackal wrote:Similar to my more 'realistic' attempt, though I couldn't resist putting in freeflow from the M1N to the new expressway.darkcape wrote:With my 'realistic' engineering hat on, here's my offering. Let's face it, we would all love a fully-freeflow junction between the A421 and M1 but with the local roads, existing A421 towards MK, and the fact the current junction setup is a botched upgrade of an older junction it's hard to improve without demolishing the whole thing and starting again (which is best but prohibitively expensive).
My option only has one new bridge, replacing the existing A421 roundabout, and building one new roundabout.
Pros:
- Expressway NB to M1 NB passes through only 1 roundabout
- M1 SB to A421 EB cuts out the existing roundabout movement
- A421 from MK to A421 NB still passes through only one roundabout
- Only one new bridge, so cheaper than other options
- Can be built around the existing road layout with minimal disruption to existing J13.
- Eexpressway remains grade-separated instead of plugging into existing A421 roundabout.
Cons:
- Roundabouts/lack of freeflow
- Lots of earthworks & land take
- Likely to be confusing for drivers
The secondary north-facing slips on the M1 were added to act as a bypass of the J13 dumbbell for traffic heading to/from M1 north. With widening the existing A421 overbridge or additional bridges these could be made freeflow.
M1 J13b.png
M1 J13.PNG
I do like the other design but it's almost so realistic that it's not realistic. The junction is already overloaded so it's unlikely that the modelling will say that more turning movements can be plugged in without mitigation via a freeflow right turn or two.
I agree that M1S<->A421N are also strategically important. But 'freeflow some new movements' is generally cheaper and less disruptive than 'freeflow some old movements and provide some new non-freeflow movements'.
Re: Oxford to Cambridge expressway
Given that the expressway will go to the A5, I'd imagine the Bedford-MK turning movements at M1 J13 would reduce a little.
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Re: Oxford to Cambridge expressway
Wow - that's interesting to know. I'd never heard of this proposal. That would be a really bad idea in my opinion given the land required which would have a severely adverse impact on the landscape, any historic assets and any environmental designations; the noise impact on residents within the vicinity of the airfield and the flight paths; the safety of residents within the vicinity of the airfield in case of the unlikely event of an air accident; and the traffic generated by the airport on the local roads (unless access is only provided via the Oxbridge Expressway or A41 Aylesbury Bypass. The Maplin Sands would minimise all these impacts except the environmental impacts which would have to be mitigated against as Foulness and the sands are designated Ramsar, SSSI, SAC and SPA. Would probably destroy a proposal for an airport here unless the impacts can be mitigated against but I'm no expert on mitigation measures and whether these could be incorporated on such a large scale proposal (my proposed airport would have 16 runways).tomuk wrote:The A41 southern bypass passes close to Cubington useful for the 4 runway airport to replace Heathrow.Philip_Baum wrote:A41 southern bypass of Aylesbury with off-line link to M40 jct 10 that crosses the Oxbridge expressway. Also I think the Oxbridge Expressway could be numbered A420 as an extension of the existing A420 from Oxford (of course multiplexing with the A34).
BucksCCMap.jpg
Re: Oxford to Cambridge expressway
Cublington (aka Wing) was one of four sites considered for a new airport 45 years ago (gosh, typing that makes me feel old):Philip_Baum wrote:Wow - that's interesting to know. I'd never heard of this proposal.The A41 southern bypass passes close to Cubington useful for the 4 runway airport to replace Heathrow.
BucksCCMap.jpg
https://en.wikipedia.org/wiki/Roskill_Commission
Has it been proposed again recently or does that picture date from then?
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Re: Oxford to Cambridge expressway
What do you think of something like the attached?jackal wrote:The M1N<->expressway movements are for traffic between the East Midlands and the South (e.g. Oxford, Southampton and the M4 corridor). These are strategically important, and the A14 is no help with them - it doesn't go in the right direction at all.Philip_Baum wrote:I prefer the earlier one without free flow to/from M1 to/from the expressway given long distance traffic would not really make such a movement from the east as the A14 (should be M14 in my opinion) is the strategic link to the M1/M6 nor from the south as the A43 is the strategic link to the M1. Realistically only local traffic would make these movements and the expense of giving local traffic free-flow should be spared. In my opinion the most important movements to give free flow to is from A421 south-westbound to M1 south-bound and M1 northbound to A421 north-eastbound. This is because the A421 (since being upgraded) now provides a link between the M1 and A1. Western M25 clockwise traffic heading for the A1 can now use the M1 to jct 13 (more direct and gets off the M25 before the northern section) and then cut across to the A1 via the A421.jackal wrote: Similar to my more 'realistic' attempt, though I couldn't resist putting in freeflow from the M1N to the new expressway.
M1 J13.PNG
I do like the other design but it's almost so realistic that it's not realistic. The junction is already overloaded so it's unlikely that the modelling will say that more turning movements can be plugged in without mitigation via a freeflow right turn or two.
I agree that M1S<->A421N are also strategically important. But 'freeflow some new movements' is generally cheaper and less disruptive than 'freeflow some old movements and provide some new non-freeflow movements'.
Re: Oxford to Cambridge expressway
Well that loop really is tight! About 40m radius according to Google maps.Philip_Baum wrote:What do you think of something like the attached?
The heavy flows (about 40% of all traffic that uses the junction) that goes A421-A421 also have to go through three or four roundabouts, compared to one at present.
Re: Oxford to Cambridge expressway
Assuming that you have the A421 coming out of MK splitting to dual carriageway then you have introduced a trailing crossover with the M1 northbound.jackal wrote:Well that loop really is tight! About 40m radius according to Google maps.Philip_Baum wrote:What do you think of something like the attached?
The heavy flows (about 40% of all traffic that uses the junction) that goes A421-A421 also have to go through three or four roundabouts, compared to one at present.
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Re: Oxford to Cambridge expressway
I'll improve this later and resubmit.jackal wrote:Well that loop really is tight! About 40m radius according to Google maps.Philip_Baum wrote:What do you think of something like the attached?
The heavy flows (about 40% of all traffic that uses the junction) that goes A421-A421 also have to go through three or four roundabouts, compared to one at present.
Re: Oxford to Cambridge expressway
The M1 NB on slip doesn't make sense - is that what you meant by "trailing crossover" Big L?Philip_Baum wrote:
What do you think of something like the attached?
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Re: Oxford to Cambridge expressway
Yes. Its a railway term. a link between two tracks where neither faces a diverge, basically. And on freeflowing roads, that link would be awfully quiet.darkcape wrote:The M1 NB on slip doesn't make sense - is that what you meant by "trailing crossover" Big L?Philip_Baum wrote:
What do you think of something like the attached?
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Re: Oxford to Cambridge expressway
https://drive.google.com/open?id=1WHAyx ... sp=sharing - my take on M1 J13 using what others have created as an inspiration, it only requires two bridges, but creates a quasi-magic gyratory that might distribute flows a bit better.
I've also removed the southern half of Bedford Road from the equation by linking it to the old A509.
The signalised crossroads on the west side of the junction could be kept simple by prohibiting right turns from the E-W route (current A421).
I've also removed the southern half of Bedford Road from the equation by linking it to the old A509.
The signalised crossroads on the west side of the junction could be kept simple by prohibiting right turns from the E-W route (current A421).
Bryn
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.
Blog - https://showmeasign.online/
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Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.
Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
Re: Oxford to Cambridge expressway
Access deniedBryn666 wrote:https://drive.google.com/open?id=1WHAyx ... sp=sharing - my take on M1 J13
Re: Oxford to Cambridge expressway
Sorry Jackal - I've reset the permissions now.
Alternatively:
Alternatively:
Bryn
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.
Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
Terminally cynical, unimpressed, and nearly Middle Age already.
She said life was like a motorway; dull, grey, and long.
Blog - https://showmeasign.online/
X - https://twitter.com/ShowMeASignBryn
YouTube - https://www.youtube.com/@BrynBuck
Re: Oxford to Cambridge expressway
Thanks Bryn. Personally I'd want to get more freeflow in if I'm paying for that extra bridge