M1-A41-A4008
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Ordnance Survey map - Alternative aerial view
Where is it?
Berrygrove interchange, at M1 J5. It connects the main road north from London to an important dual carriageway route bypassing Watford and another important dual carriageway route into Watford.
It was spotted by Keith Mason.
What's wrong with it?
It's chronically, tragically, tear-jerkingly, desperately under capacity. Basically we have one roundabout to connect three dual carriageways heaving with traffic - or to put it another way, the interchanging movements between fourteen busy traffic lanes are carried out by three shared lanes. It's not pretty.
Why is it wrong?
It was never designed to be a particularly heavily-used junction at all. When it was built, the A4008 didn't exist, and so the very unusual double roundabout interchange design existed to let traffic hop between the M1 and A41, something that was possible further north and south of this junction. It did the job quite nicely. Then, some bright spark built a new dual carriageway from the centre of Watford to the M1. Not a bad idea. The problem came when they saw a lovely roundabout with plenty of space to add a dual carriageway in. Add in the fact that Watford town centre is so busy that traffic regularly stacks back on the A4008 right out to this junction and you're starting to get the picture.
What would be better?
A very good question. The fact that the M1 and A41 are running parallel here is not good news in terms of junction design, and the fact that no remedy to the problem is even being considered by those in charge suggests ideas for this one are thin on the ground. I'm certainly having a hard time coming up with anything.
Right to Reply
E-mail me with your comments.
Simon Hollett has an idea:
A fairly easy improvement would be to make a link at the middle of the roundabout to form a roundabout over the A41, and a junction similar to the M4/M32 one above the M1. Then it will be cheaper to put more lanes on the roundabout (say giving 3 or 4 total) as the number of bridges has halfed. It's a fairly rubbish improvement, but it's something.
Paul Berry disagrees:
The problem with the interchange isn't the capacity of the roundabout, or the A4008 (which is a relatively recent addition), but the immediate proximity of the on and off slips to and from the M1 and A41 - even with part-time lights on all the slips there are two points of conflict either side of the axis parallel to both roads.
David adds:
I have used the junction quite often, to transfer between the M1/A4008. I have never once experienced a jam of the type you are describing! The A4008 allows you to get into Watford from the M1 in less than 5 minutes. It used to take up to 30 minutes, via Bushey, depending on often hideous traffic around the retail estates outside Watford.
Brian Freeman is fine with it:
I use this junction all the time and at all times of the day, week and year. The worst I have ever known it is for the traffic to back up a bit down the various slip roads and down the A4008, the only exception being if there is an accident on any of the roads.
At rush hour, it beats Bushey Arches as a way into Watford from places like Edgware and Stanmore.
It's definitely a weird junction but generally works quite well for me.
David finds a few problems:
Part of the problem at this junction is the poor road markings leading to dangerous change of lane. It is also the responsibility of Hertfordshire CC rather than the Highways Agency because of the access to the A41 and A4008.
If Herts could pull its finger out, a few cans of white paint could improve the traffic flow and safety on this junction considerably. There is also the problem of the lights coming onto the roundabout from the A4008 from Watfrod which are not very responsive to the traffic flows. Again Herts CC say there is nothing wrong.
Gary Mason shares his thoughts:
The trouble with this junction is not that it is a dangerous all the time - it is dangerous only occasionally.
The greatest fault is that the carriageway has no lane markings save at the corners and no lane indicators (e.g. A41 or M1 South) other than at its Southwest corner. The danger caused is that traffic wishing to join the M1 South takes either the centre lane or the inside lane as they go round the roundabout. Unfortunately, traffic from the M1 North to any exit, also takes either the inside lane or the centre lane.
Therefore, if traffic from the M1 North to, say, the A4008 takes the inside lane, and traffic from the A4008 takes the centre lane to the M1 South, the former will be travelling across the M1 South junction as the latter is driving across it.
A colleague who is an accident investigator has a very fine template of this junction to copy into regular reports.
Sue has an idea:
The A41/M1 junction at J5 of the M1 could easily be improved by NOT having the A41 link here and changing the layout at M1 J4, a few miles down the A41. This would leave just the A4008/M1 link at M1 J5 which would be easy.
Neil Symons has other problems:
Never have I seen the A4008 traffic backed up to the motorway. The main issue with it is the traffic lights. 1) They should be part time not full time as the amount of traffic at night is small enough to not need them, 2) If leaving the M1 southbound the green sequence is far too short which in rush hour tends to leave the slip road full, 3) There are too many sets of lights (one for each join) to go from A41 southbound to the A4008 you have to go through 5 sets of lights. A good example of limiting sets of lights is J19A of the M25 just 3 miles away for the M25,A41,A411 junction there is one set where the knock on effect of those lights make the junction flow very well.
