Lack of long-term planning for M50 upgrade

MT

When the M50 was first envisaged why didn't the planners reserve enough land around each junction for adequate free flow upgrades in the years ahead? I've seen the proposed junctions in the upgrade plan and few appear to be anyway near adequate. In particular the M50/N7 junction could have done with something like a four level stack interchange – these being the most free flowing of all junction types when two motorways cross.

Of course there isn't the space for one now. Which is ironic considering that the Netherlands (the world's most densely populated country) at least managed to build a few of these while the Republic with one of Europe's lowest population densities hasn't got the space.

Did planning actually take place in West Dublin or was it always handled by Liam Lawlor types? If ever there was a missed opportunity...

Dutch (2nd down), American and British four level stack junctions.

I imagine these are extremely expensive but it’s the only sort of junction that would be able to cope in the long run with congestion where the M50 and N7 meet, and possibly some other high capacity junctions. But it’s all academic now as the space was never reserved!

MorningStar

I would like to point out the difference between what planners do and what actually happens. As illustrated by the reports about planning yesterday and today. The planners don't make the decisions, the politicians do.

The politicians focus on vote generators not what is the best thing to do. So in actual fact the people to blame are the public for voting on who fixes the cracked cirb in front of their house.

Note that people going on about the toll bridge and insisting on the removal without out any real logic for payment for existing contract. THe prooblem is more to do with unrealistic public expectation than thoses doing what is desired.

Imagine a politican going for office saying "I do what is best for everyone but you won't like it please vote for me"

John R

Except the N7 isn't a motorway. There are controlled junctions close to the interchange so free-flow isn't an option anyway.

Bluetonic

MT wrote:

Which is ironic considering that the Netherlands (the world's most densely populated country) at least managed to build a few of these while the Republic with one of Europe's lowest population densities hasn't got the space.

Not to go off topic but Monaco is the worlds most densely populated country with a densety of 16,620 people/km2.

The Netherlands is only the 15th, with 395 people/km2.

As you were.

Alun

Well it's the most densely populated 'proper country' in Europe. This is not including places like the Vatican City, or places like Gibraltar, Channel Islands, Monaco etc whose 'population' is artificially inflated by virtue of their being tax havens of one sort or another. If everyone who claims to live in Monaco all went there at one time it'd slide off into the sea under the weight.

murphaph

The N7 ends at the Red Cow and city bound traffic is really supposed to head along the M50 to join the N4 as it is a far superior road owing to the Chapelizod Bypass.

The only real problem I have with the proposed red cow is the apparent lack of a freflow off slip for N7 southbound traffic heading north on the M50. As the Naas Rd inbound is only a regional road with many sets of lights it is not going to make a lot of difference.

We really shouldn't be encouraging car commuting 'across' the M50 so it's ok IMO to keep the freeflowing movements between the M50 and all outbound sectons of the trunk roads, whilst not going overboard and spending ridiculous sums to provide freeflow slips inbound (onto roads which are not gong to be free flow anyway as they are junction laden and always will be). I have a problem with the N2 as it won't be freeflow in these directions. The N3 and N4 will be fully freeflow between the M50 and trunk roads 'outside' the M50.

MT

Murphaph, have you noticed that in some of the proposed junctions some traffic will effectively have to merge in the fast lanes?

The problem I have with junctions that are deliberately designed to exclude citybound traffic from their free flow design is that while well intentioned this could in itself lead to a reduction of capacity in the other directions. If traffic going into the city - as it inevitably still will - cannot exit the junction quickly this may result in this flow of vehicles clogging up other parts of the junction thus lowering its capacity in all directions.

My thinking behind a total free flow junction like a 4 level stack is not that all the directions from it will ever be able to fully make use of its extra capacity but that it should have a better chance of clearing all the traffic from this point of confluence. Put simply, building a junctions designed to keep four directions moving could well in the long run be the best approach to keep the three that are actually needed flowing freely.

Murphaph, this is probably a topic for the signage thread, but have you seen any of the proposed signs for these new junctions?

murphaph

In an ideal world MT, they goons would have planned it properly and we could just used cheap and simple 4 leaf clovers (not as much throughpout as a 4 level stack of course!). Corruption and bad planning put paid to that.

As for signage, haven't seen a peep though I notice the new gantry signs on the M1 near the airport adhere to the rules and are perfectly clear.

spacetweek

murphaph wrote:

In an ideal world MT, they goons would have planned it properly and we could just used cheap and simple 4 leaf clovers (not as much throughpout as a 4 level stack of course!). Corruption and bad planning put paid to that.

Leaving enough room for clovers would have used so much land they would have turned all areas of west Dublin close to the M50 into an LA-style concrete nightmare. And I suppose they didn't forsee so much traffic using the road.

As for 4-level stacks, if you look here, and scroll down a bit, you'll see that, in Austin at least, one stack interchange costs $125M - so if all major junctions on the M50 were constructed to this standard, you'd be looking at $625 million - surely over-extravagant by anyone's standards!

MT

Leaving enough room for clovers would have used so much land they would have turned all areas of west Dublin close to the M50 into an LA-style concrete nightmare.

From a driving and safety point of view I'm not a fan of clovers either. The curviture of the connecting roads means they're slow to use - as will be some of the semi-clovers proposed for the M50 - and depending on the design they can cause dangerous weaving.

As for 4-level stacks, if you look here, and scroll down a bit, you'll see that, in Austin at least, one stack interchange costs $125M

They're certainly expensive, that's for sure. But my original post refered to simply leaving enough land around the junctions vacant so that such a design might one day be utilised if necessary. Not that all junctions should be 4 level stacks or that any more than one should be build during a particular upgrade. My beef is why wasn't the most basic of planning procedures followed - restricting development in the vicinity of the junctions so that the potential to upgrade them significantly remained. Not that any should be 4 level stacks but that the space would be there if that turned out to be the standard of infratructural capacity required.

Having said that I do think the N7/M50 would have been a candidate.

murphaph

MT wrote:

My beef is why wasn't the most basic of planning procedures followed

darkman2

A couple of points:

a) The prospect of 4 tier junctions dosnt arrise for the M50 simply because the N roads on the city side are not free flowing. Hence the lack of freeflow slips from the M50 - city on some of the proposed changes to the interchanges. The exception being the M1, itself getting a 3rd lane to accomodate the Port Tunnel.

b) Its all well and good talking about LA, however a fundamental point has been missed and thats the asthetic look of the interchanges. What I mean is that 6 tier junctions may look spectacular in the 'Sunshine State' however under our gloomy skies I can gaurentee that the same hideous looking flyovers in the UK would transpire here if we went down that route. The N7 interchange will be Three tier.

c) I hear alot of ppl saying there is 'not enough space'. This is nonsense, give an engineer the funding and anything can be achieved.