Oxford to Cambridge expressway

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jackal
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Re: Oxford to Cambridge expressway

Post by jackal »

6637 wrote:
jackal wrote:
6637 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.
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.png
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.

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.
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.
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Re: Oxford to Cambridge expressway

Post by Bryn666 »

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).
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Re: Oxford to Cambridge expressway

Post by darkcape »

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 J13 Layout
M1 J13 Layout
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Re: Oxford to Cambridge expressway

Post by Philip_Baum »

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
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.
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Re: Oxford to Cambridge expressway

Post by jackal »

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
Similar to my more 'realistic' attempt, though I couldn't resist putting in freeflow from the M1N to the new expressway.
M1 J13.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

Post by Philip_Baum »

jackal wrote:
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
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 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.
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Re: Oxford to Cambridge expressway

Post by jackal »

Philip_Baum wrote:
jackal wrote:
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
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 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.
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.

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'.
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Re: Oxford to Cambridge expressway

Post by si404 »

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

Post by Philip_Baum »

tomuk wrote:
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).
The A41 southern bypass passes close to Cubington useful for the 4 runway airport to replace Heathrow.

BucksCCMap.jpg
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).
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Re: Oxford to Cambridge expressway

Post by wrinkly »

Philip_Baum wrote:
The A41 southern bypass passes close to Cubington useful for the 4 runway airport to replace Heathrow.

BucksCCMap.jpg
Wow - that's interesting to know. I'd never heard of this proposal.
Cublington (aka Wing) was one of four sites considered for a new airport 45 years ago (gosh, typing that makes me feel old):

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

Post by Philip_Baum »

jackal wrote:
Philip_Baum wrote:
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 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.
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.

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'.
What do you think of something like the attached?
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M1 jct 13 remodelled.png
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Re: Oxford to Cambridge expressway

Post by jackal »

Philip_Baum wrote:What do you think of something like the attached?
Well that loop really is tight! About 40m radius according to Google maps.

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

Post by Big L »

jackal wrote:
Philip_Baum wrote:What do you think of something like the attached?
Well that loop really is tight! About 40m radius according to Google maps.

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.
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.
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Re: Oxford to Cambridge expressway

Post by Philip_Baum »

jackal wrote:
Philip_Baum wrote:What do you think of something like the attached?
Well that loop really is tight! About 40m radius according to Google maps.

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.
I'll improve this later and resubmit.
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Re: Oxford to Cambridge expressway

Post by darkcape »

Philip_Baum wrote:
What do you think of something like the attached?
The M1 NB on slip doesn't make sense - is that what you meant by "trailing crossover" Big L?
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Re: Oxford to Cambridge expressway

Post by Big L »

darkcape wrote:
Philip_Baum wrote:
What do you think of something like the attached?
The M1 NB on slip doesn't make sense - is that what you meant by "trailing crossover" Big L?
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.
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Re: Oxford to Cambridge expressway

Post by Bryn666 »

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).
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Re: Oxford to Cambridge expressway

Post by jackal »

Access denied :(
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Re: Oxford to Cambridge expressway

Post by Bryn666 »

Sorry Jackal - I've reset the permissions now.

Alternatively:
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M1-J13.png
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Re: Oxford to Cambridge expressway

Post by jackal »

Thanks Bryn. Personally I'd want to get more freeflow in if I'm paying for that extra bridge :driving:
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