A3 - A31

Hog's Back

Where is it?

At the southern end of the old, narrow and congested Guildford Bypass, where the A31 parts ways with the A3 and heads off to Hampshire.

What's wrong with it?

It's a free-flowing junction between two busy dual carriageway A-roads. Surely that's a good thing!

Well — yes and no. Yes, it's a good thing, because if it was a set of traffic lights or a poky little roundabout that connected the A3 and A31, then I'd still be complaining and banging my fist on the desk with righteous indignation about the fact that Something Must Be Done.

No, it's not such a good thing, because it was designed in the mid-1930s and exists as much because of the geography of the area as anything else. As a result it's full of tight corners, blind summits and sudden merges where you can't see what's coming — not just on the sliproads, you understand, but on the mainline A3 as well. Yikes.

Why is it wrong?

It's very very old, silly. Not that old is automatically bad, of course. There are some lovely old things in the world. If you have grandparents you'll know just what I mean.

In this case, because it's old it was built without the design standards we would employ today which mean that, for example, coming south on the A3 the right turn as the sliproad leaves is completely blind for traffic in the right-hand lane.

The engineers of the 1930s never meant for it to be quite like this, you understand. No — in their day, what is now the east-to-north sliproad was a two-way road with a T-junction at each end, so anyone turning between the A3 and A31 would have gone that way. The south to west sliproad was an innovation of the 1970s, at which point it became possible to go fast around here, and that's where the problem lies.

If you dawdled along here at 40mph, took it nice and steady through the merges and corners, you'd be fine. Time to see what's coming and enough visibility to cope with it. But then if you dawdled along here at 40mph you'd be rear-ended by an impatient Surrey BMW before you'd driven a hundred yards, so really that's not such a great option.

What would be better?

This junction — and, indeed, the whole southern half of the Guildford Bypass — needs help. Just to the north there's some flat junctions with traffic crossing on the level. Frightening.

Major reconstruction is unlikely, because the people living nearby would never stand for it. But it should at least be possible to lengthen the merge from the A31, shouldn't it?


Right to reply

Andy K 6 March 2011

This junction is a love-hate thing. You love it when you are travelling south on the A3 through slow moving traffic on the Guildford bypass, which is woefully under capacity and has awful junctions, when you see this junction, knowing both roads past it are free flowing.

The hate comes when you have ANYTHING to do with this junction which doesn't involve just carrying on down the A3. The A3-A31 slip road has scary tight bends and confusing signs. The A31-A3 slip throws you onto the A3 with very little chance to merge. And then of course there is the whole 'sudden end' of a 60mph road crashing into Guildford just after this!

The Hog's Back itself is quite a nice drive - it like you are driving on a wall, with drops on either side. The road surface needs a lot of work on it - its too bumpy for a 60mph road, and the gaps between carriageways need to be filled up to make this road truly safe. Sadly though, the junction is probably going to remain as it is, partly to to with the geology of the location. What really needs to be done is the widening of this part of the Guildford bypass - but we know that will NEVER happen...

A303paul 6 March 2011

For years in the 1980s the south to west slip was closed for some reason and the traffic lights got reinstated. Boy was that fun.

Having had to use this junction for a few years now, I'm getting used to it, but, for anyone heading South on the A3, the big shock is the fact that the 'obvious' route if you are in the left hand lane is up onto the A31.

This is so much of a problem that there are signs on the A31 as to how to rejoin the A3. I'm not sure that much could be done in the space available though.

Also spare a thought for people heading along Down Lane, the West to South arm of the junction. What you don't realise unless you are unfortunate enough to meet another car is that the sliproad is bi-directional until right before the merge with the A3...

Timbo 7 March 2011

I agree this junction is way below spec for the traffic it carries, and part of the problem is that it is at the crest of the Hogs Back which inevitably affects sightlines.

Grebbsy 8 March 2011

It isn't every Bad Junction which can boast to have claimed the life of a Formula 1 motor racing driver, but this one can (Mike Hawthorn in 1959).

Ian Saunders 18 March 2011

Hi Chris.

Go on, I'll bite. I like the junction. No that's too weak. I love the junction! Not in a buy-it-flowers and take-it- to-a-movie kind of way, but I do use and enjoy it whenever I'm heading out to the South West.

I'm happy to admit I don't use it much in rush hour, but it's not always at 5 am either. When I've used it I've never once stopped and usually don't have to slow down either (and no I don't have a BMW).

You mention youself that it's free flowing and not a light or roundabout in sight. For me that makes it a great junction. So you have to make people brake a bit coming onto the A3 from the A31. It's near London and people should be used to assertive driving.

Jack 11 April 2011

Well, I'm probably not going to be very popular, but what on earth's the fuss all about?? The speed limit is 50 here, and all you've got to do is drive defensively!

Bibhas Neogi 7 September 2011

The A31 slip road from the A3 towards Farnham was built in or around 1970. Before that the route to Farnham at this junction here was through the current A31 eastbound on-slip which was then two-way. You were able to turn left from the A3 onto this two-way road until the early 90s when this was stopped up and the the A31 on-slip was made one-way single lane for safety. A Sign was put up on the A3 advising motorists to take the B3000 as there was no left turn ahead from the A3 to A31 Hog's Back.

The A31 on-slip merge with the A3 had been lengthened in the mid 90s. The scheme to widen the A3 from this junction to Dennis roundabout (A322) has been suspended following cuts in the roads programme. I have outlined my ideas of how this junction could be improved on my website which may be found by searching for 'revampguildfordgyratory'.

David C 16 July 2015

Coming off the A31 onto the northbound A3 is a very risky business indeed! I have lived around these parts all of my life and witnessed the various junction modifications in my 38 years of driving but if one more were surely needed it's to allow safer access onto the northbound A3 from the A31.

The problems are two-fold as I see it: first, there is the problem of having good visibility over one's shoulder when attempting to come off the slip-road and north-bound traffic on the A3 popping over the brow of the hill just before the junction and often exceeding the 50mph limit. This could be very safely and cost-effectively remedied by doing exactly what has been done on the north-bound A325/A323 junction between Aldershot and Farnborough only some 10 miles away in NE Hampshire. That is to force northbound A3 traffic over to the off-side lane and allow the joining A31 traffic to join and merge with impunity as it does on the A325 with joining traffic from the A323. As the meerkats say "simples"!

Derek W 22 September 2015

Mainly to clarify or correct some dates, and add a liitle extra info':
The A3 to A31 slip road (over the newer bridge) was built in the mid-late 1970s - prior to that there was a signal controlled right turn from the southbound A3 on to the (then) two-way northern slip road. However it was closed for an extended period in the early 1990s when major defects in the 1970s bridge had to be rectified - at that stage all north-to-west traffic was diverted via the B3000. At Puttenham, the B3000 / A31 westbound sliproad junction was modified with a temporary mini roundabout to try to help traffic join the westbound A31.

The A3 / A31 slip road remained two way (allowing traffic from northbound A3 to turn left) until the present layout was built in around 1989, as a late addition to the Compton-Shackleford dualling (which extended the Guildford dual-carriageway section southward to just short of Milford, including grade-separating the junctions at Compton and Hurtmore).

The current layout means that the B3000 between Compton and Puttenham is de facto part of the trunk road network, which has never been acknowledged by HA / HE. The junctions at each end of this section were never designed with this in mind, and are heavily overloaded as a result, however neither HA/HE nor SCC will fund improvements.

Miles T 1 January 2019

There are various local legends about the junction being haunted, and also cursed (along the lines that if the bridge that is part of the junction is changed then bad things would happen in the world...)

But perhaps not quite as "haunted" as this now famous junction in the USA:

Which is really just an optical illusion that occasionally causes accidents when tourists want to try out having their car push up a hill by a ghost

Martin C 8 January 2019

"This could be very safely and cost-effectively remedied by doing exactly what has been done on the north-bound A325/A323 junction between Aldershot and Farnborough only some 10 miles away in NE Hampshire. That is to force northbound A3 traffic over to the off-side lane and allow the joining A31 traffic to join and merge with impunity as it does on the A325 with joining traffic from the A323. As the meerkats say "simples"!"

Couldn't be further from the solution, the traffic A3 northbound weekday mornings tails right back to Milford. This is not even the Hog's Back interchange causing the problem, it's the Cathedral/Hospital exit a mile or so north.

Chris Mills 8 August 2020

@Martin C. Actually it's both. The A31/A3 Merge is a bottleneck and is compounded by Cathedral turn slowing the traffic on the A3 just after the merge, often causing tailbacks to the merge itself.

The real solution is a new Guildford bypass. The problem is where to put it and dealing with the NIMBYs With that done the old A3 could be downgraded (perhaps even singled) as the through route would be the new bypass and the old road would only be needed for access to Guildford

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