Picture in this linkie - use the find function with "1271".

The 657 (Shepherds Bush - Hounslow) and 667 (Hammersmith - Hampton Court) both used this roundabout and were in the last tranche to go, in 1962.

I believe the very last new trolleybus wiring to go up in London was probably in connection with the remodelling in Blackwall during construction of the second tunnel - the trolleybuses in the area ceased in November 1959, before the tunnel work was completed. The re-arrangement at Hammersmith when the Butterwick opened was around the same time.

Great pictures on that web site, but I don't understand why you would have so many on one single page. That's going to take time on slow connections.

If a non-complaint LEZ vehicle were to travel along the M4 into London and wishes to avoid the charge and wants to turn around, can they use Junction 4 instead of Junction 3 (as it would then be quicker to head back out of London). Or are there cameras on the slip roads at Junction 4?

However, I find Junction 4 quieter than Junction 3. The A312 at Junction 3 seems a much busier road than the A408 at Junction 4, and there are more lanes at the roundabout at Junction 4 than Junction 3.

Yes junction 3 is rammed at all hours whereas junction 4 seems okay.

Maybe it's all the u-turning stinky trucks that's making the difference.

Are there large quantites of these? I can understand the odd one, but if you are delivering in London you are going to have to pay the LEZ charge anyway, and if not you'll likely be using the M25, surely?

Thanks for that link - I've just had a very enjoyable twenty minutes at the site. Wonderful not just for the buses but also the London street scenes. Interesting picture towards the bottom of those bridgeworks in 1966 for the coming of M1.

Signs now appeared saying the road will be closed every night from 14th may until 20th July between 22.00 and 6.30, a total of 9 weeks. Due therefore to finish 5 days before the Olympics.

I presume these are for repair works , best not over run then. Bet there's an early completion bonus.

For the concrete section, what would happen if you cut a hole in the middle of an elevated section sufficiently large to sink a new peer in the centre of an existing span? How much would it weaken such a structure?

Would this allow you to keep the A4 open as a diversion while constructing a replacement elevated section immediately over the top of the existing one? The old structure acting both as protection for the A4 carriageway below, and as a construction platform during work. Perhaps with a movable balcony extending over the third lane? Then, with new elevated section complete and in use as a replacement route, somehow demolish the old structure from below with temporary closures and diversions of A4?

Probably totally impractical, but it was the only way I could see of possibly keeping one or other of the A4/M4 open at all times without constructing a completely alternate route (e.g. tunnel).

You'd have some serious problems trying to replace the viaduct along there. I can only see one workable option and that is the total closure of the motorway to remove the viaduct bit by bit.

It'll be very, very, messy whilst it's done. Best get Gypsy Corner and Savoy Circus sorted out...

Think bigger... The replacement strategy should be to build a whole new viaduct alongside the existing M4 giving 12m of available road width to run as a S4 at 40mph, the demolish the existing viaducts and build a matching viaduct alongside, transfer one direction from the first new viaduct and open as a D3 managed motorway at preferably 50mph in the tight sections and 70mph further out of central London.

There will be some cost pain, but leaving the existing structures in place isn't a long term solution.

That sounds similar to the A55 replacement in Marseille except that was flyovers into new tunnels.

Given the M4 runs in the centre of the A4,(itself lined by 30s development) any new viaducts on either side will either be in (and cover) someones front garden and or require extensive propety demolition. Can you honestly see that being remotely aceptable in this day and age regardless of the traffic situation?

Yes Phil I can... The day of the NIMBY has gone, we are in a new age of third and fourth runways at Heathrow, High Speed Rail corridors... There comes a time when the need of the majority overcomes the sentiment of the minority. Justification was slim back in the day, but the factors are multiplied the longer the problem goes on... Bring on the new concrete era !!!

Has anyone proposed double-decker roads where extra capacity is needed but no extra width available ?

The engineering is no doubt involved and expensive but surely needs consideration.

Building a double decker viaduct over an existing crumbling viaduct would in my experienced engineering view be more costly than demolishing relatively low value homes, time sheds and third rate office accommodation. There are some higher value properties along the route, which could be planned around.

The same question has already been asked a few times in the US, with the Boston Big Dig and Alaskan Way viaduct. In Boston they opted for a tunnel, but it ended up costing about $14bn (albeit for a longer length). With that in mind, and bearing in mind the current likelihood of any major investment in road infrastructure, I think it's fairly likely that the HA will do almost anything to prolong the life of the M4 viaduct, even if it means building a separate secondary supporting structure under and around it, as other than quickly becoming life expired there is no real need to replace it.

I wonder how feasible it would be to use a similar technique to stadium roofs, where steel supports wrap around the back of the structure - or perhaps even steel arches rising from either side of the A4? It could certainly be an impressive architectural statement.

Would the A40 be the diversion route?

Diversion route? It's the only route.

Well given that the A40 is already at or near capacity, they might as well send everything down the A4. As bad burnt as scolded, so to speak.

The M3 gantries northbound recommended traffic to continue into London via M3-A316 rather than M4.