Hammersmith Flyunder? Boris Johnson wants to send London's traffic underground

Isn't the ground in London full? Part of the reason the Crossrail tunnels had to go quite deep is that London is already full of shallow-level tunnels.

Is there space under Hammersmith, or is the proposal just to put a lid on top of the existing roads and put the pedestrians and bikes on top of that?

Boston's Big Dig (done with a fair amount of UK expertise) is not a bad comparison, being a traffic-clogged major city with legacy traffic routing issues. Mind you, it's right on the ocean, too. And if there was only one death (which I recall was from a faulty bolt installation) that would be excellent.

First, of course, we should be encouraging London-bound people to leave their cars (which I accept are a necessity for many) at suburban "Park & Ride" satellite stations all around the M25 corridor. Land is cheaper and more available and there should be an attractive "all day parking" add-on to fares from these stations of £5/day or so. yes, it would be subsidised, but it's better than the alternatives.

I'm a west-ender so can only speak about the Hammersmith and Chalkers Corner options with any degree of knowledge, but the Flyover doesn't really do much, does it? And it's about to fall over. Just before the flyover is that horrible Hogarth roundabout with its own "temporary" flyover, and before that several sets of traffic lights. Yes, I know - traffic lights on an "expressway". It's just a wide street, and I think sinking it (think of Brussels, too) is a great idea, but don't expect any improvement in journey times.

I really do wonder who all is driving in and out of London every day. I know a builder from Berkshire who worked in Chelsea for over two years, and he drove in and back every day, despite living near a train line right into Paddington. Obviously he had tools to worry about, but the hassle of parking and driving every day? Crazy. Individuals make odd choices and we need to encourage them to make better ones. Basing train fares on what a banker can afford is not the place to start (builders already have a van - may as well use it then).

I also seem to recall the existence of several Tube lines in the vicinity, just to make digging interesting, and a large river.

pikeamus wrote:

My understanding was that large tunnels for motor vehicles have a very negative impact on the air quality in the areas where the tunnel terminates, worse than having open air traffic. I'm sure I remember another story about some tunnel already in place in London, and the particularly startling levels of childhood asthma in the immediate neighbourhood. Can't remember quite enough detail to find the story quickly. Something to think about anyway. Better off just reducing car usage as much as possible (and encouraging a switch to electric for that matter).

Well, the solution is to have tunnels that don't terminate. Just put a network of tunnels down there and let the petrolheads drive round-and-round interminably to their heart's content.

I suppose, in the interests of compassion, some sort of air filtration system would have to be provided (scope for some kind of carbon-capture?), but apart from that, just leave them to it.

Being _really_ charitable, you could provide car parks down there and stair-cases for entry and exit (but I fear that might be conceding too much).

Used the 2 cycles tunnels in and around Rotterdam last year. Thought they worked extremely well. Note: had security at both ends.

My understanding was that large tunnels for motor vehicles have a very negative impact on the air quality in the areas where the tunnel terminates, worse than having open air traffic. I'm sure I remember another story about some tunnel already in place in London, and the particularly startling levels of childhood asthma in the immediate neighbourhood. Can't remember quite enough detail to find the story quickly. Something to think about anyway. Better off just reducing car usage as much as possible (and encouraging a switch to electric for that matter).

I'd like to see this developed with a heavy focus on freight. It seems just on the edge of possibility to have a city where HGVs never drive more than 1000m on the surface...

Most of the Hammersmith flyover runs directly above existing surface level major roads, so unless these are going to be built over at some point I don't see how the tunnel will have much benefit. All the access and egress routes still need to be there, unless the purpose is for the road to bypass Hammersmith town centre completely.

We have at the present time possibly the biggest pool of tunnelling talent ever created/assembled. I am of course talking about Crossrail.

At the end of Crossrail this talent will disperse and the opportunity will be lost. If we are going to undertake these schemes and others such as cycle tunnels under the Thames then we have to start the planning now.

Only a true fool could look at the Big Dig and go "I want to replicate that". He might as well go to Seattle and take inspiration from "Big Bertha".

Anyway, most of this doesn't have even a sniff of a costing for it. Which belies what it may be- something to make the motor traffic lobby think he's thinking about them in the wake of upsetting them over cycle superhighways.

That, or he needs to dig lots of tunnels so that spoil is generated to build Boris Island, as he doesn't accept that that is dead, too.

Hammersmith flyover is a blot on the landscape and the gyratory is dangerous to cycle. Getting rid of it would be a good thing.

Well I hope it's managed better than the Boston "Big Dig"
That took something like 15 years to complete and as its says on Wikipedia "The Big Dig was the most expensive highway project in the U.S. and was plagued by escalating costs, scheduling overruns, leaks, design flaws, charges of poor execution and use of substandard materials, criminal arrests, and one death"

Why not put cars underground and people walking on the ground. You have more space for parks, trees and cycling/walking paths. while you have a lot of space underground. I know it is not viable, but Japanese underground roads are already used and they plan to be build more of them. Would be nice to see London with some nature to it, not just the roar of engines.

I know all the focus is on the Hammersmith flyover, but I really want to know what exactly the "decking" is over the A3. I can't escape this mental image that it's someone's weekend DIY project, and it's going to have a few loungers and maybe a patio heater for the winter.