Where is it?
The southern end of the A23's motorway-like section, on the northern fringe of Brighton.
What's wrong with it?
It's just all wrong. The A23 is a motorway standard road which has come from the end of the M23 and whizzed traffic on two and three lane sections all the way to here. And it ends at a roundabout. As if this weren't bad enough (and it's not), to get anywhere from there requires turning left, going uphill, passing a right turn, going round one or two more roundabouts, and only then joining the A27. It's cumbersome, slow, and what's worse it's practically brand new.
Why is it wrong?
It's basically a combination of a railway line, steep hills and a built-up area. But can't space be found for a left turn from the A23 to A27 eastbound at the very least? Apparently not. The wider problem seems to be a tight fist with regards to cash.
What would be better?
How about some free-flowing links? Yes, this junction is sited in a steep and hilly area, pushed up against the suburbs of Brighton. But a left turn for southbound traffic would squeeze in, and after that you can get rid of the dumbell interchange over the A27 because north-side links aren't needed. Close off the right-turn on the linking road for an almost-trumpet, keeping the roundabout to access the A23 into Brighton.
Right to reply
You're right, it is a mess. Unfortunately, as you quite rightly point out, it is slap bang up against the Brighton suburbs. It is also on the southern limit of the proposed South Downs National Park, so improvement to the situation is nigh on impossible. It is effectively the best of a bad bunch.
Added to this, just to the west of this junction is the junction with Dyke Road (another dumbell), a major arterial route into and out of the centre of Brighton. So a lot of traffic joins the A27 here. The feeder lane from the Dyke Road junction, suddenly becomes the slip road for the A23, so just beyond this junction there's a lot of weaving and lane swapping going on, between those wishing to move left to gain access to the A23, and those wishing to follow the A23 east.
This junction is a considerable bottle neck, particularly at peak times. Owing to the poor traffic flow there is a knock on effect, on to minor roads in the vicinity.
There are limited North/South routes over the South Downs and rural roads are heavily used, as poeple endeavour to avoid this junction. Additionally the A23/A27 junction is part of the principle route from the South Coast to London. Traffic from Eastbourne and Newhaven Port are directed to use this junction as the principle route North.
Once the Beddingham road works, near Lewes (8-10 miles East) are completed this junction will become a greater bottle neck, traffic diificulties east of Lewes will have been alleviated moving the problem at this junction.
I am surprised no-one has commented on what I consider a major issue. On leaving the A23 southbound there are 2 lanes available, left for A27 westbound and right for A27 eastbound. Just after veering off these are joined by a 3rd lane coming from the roundabout giving 3 lanes up to the A27. At the top the left lane is correctly arrowed to curve away to join the A27 westbound leaving the other 2 lanes both arrowed as straight ahead into the roundabout. Problem is, the exit from the roundabout is 2 lane bi-directional, giving traffic entering in the outer lane nowhere to go except head on to oncoming traffic unless doing a quick merge without warning or a loop around. Barmy and dangerous.
I've found that when travelling west on the A27 from Lewes and want to travel north on the A23, if I see traffic backed up on the A27 for the A23 slip I will travel up to the next junction (Devils Dyke) and will use the roundabout there to use the A27 eastbound and get on the easier slip road for the A23 northbound. I've done this route many times and tried it out with a friend who took the turning for the A23 off the A27 where as I went and did the Devils Dyke manoeuvre and I was ahead of him on the northbound A23 by just 3 minutes. Something worth bearing in mind.
I discovered another major flaw with this junction when negotiating it during the recent heavy snow. Heading north out of Brighton I needed to join the A27 westbound. To do this you have to travel from lane 3 to lane 1 whilst heading uphill off the roundabout. This would be fine apart from the fact that the A23 Southbound has two freeflow lanes up to the junction, causing vehicles on the inside lanes to be travelling much faster than that in the outside lane. It's a most unnerving experience to find a lorry shoot past you on the inside as you prepare to change lanes!
After recent work where they tried free flow from A27 WB which lasted just a few weeks the latest is to mark the three lanes coming from the A23 roundabout as A27 wb, A27 Eb Local traffic (ie doubling back to head down mill road). However both times I have come off the A27 EB to cross over and head down mill road cars heading from the A23 to A27 eb are still using both lanes and again trying to squeeze into one across the bridge. I've also been crossing the bridge and had two cars coming the other way using both lanes.