M1 - A405

See this location on SABRE Maps

Name
Waterdale Interchange

Where is it?

Junction 6 of the M1, the connection between the main road north and the North Orbital Road. The latter has been replaced by the M25, so it should be a simple affair, but it's not.

It was nominated by Stuart Parks.

What's wrong with it?

It's a pair of looped sliproads; a parclo to use the jargon. That's not a fault in itself. In fact it looks quite nice on a map. The problem is that — for some reason best known to themselves — the men who planned the M1 decided to do away with the intelligent design work they had showcased on the rest of the route, and chose to make the weediest excuse for a junction possible at this location.

Its sliproads are single-carriageway, meaning that — under motorway restrictions — you are travelling in one narrow lane with oncoming traffic to your right. They're tightly curved too, making anything more than 30mph tricky. But that is a mere aside compared to the rather incredible piece of design that connected this junction directly on to the existing housing development at Bricket Wood. As a result, the sliproad connecting to the M1's southbound carriageway has two at-grade junctions on it with residential streets. There are houses on it. There are driveways leading on to it, for heaven's sake. The sharp curves obscure the junction with Mount Pleasant Lane, and the other access is dangerously close to the sliproad's end on the A405. The result is that this is not exactly a stress-free interchange.

There's also the niggling complaint that when the M25 was built, it came with another Bad Junction immediately to the north, M1-M25, which means that anyone travelling between the M1 to the south and the M25 to the east is routed through this interchange. As if it didn't have enough problems already.

Why is it wrong?

Picture the scene. It's the 1950s, and you're working in the design office for the M1's first phase. There are no other motorways in the UK yet, and the only other one at an advanced stage of planning is shorter than the distance between your civil service issue desk and the canteen. You're probably wearing a very thin tie and those black-rimmed spectacles that everyone wore in the fifties. You are, without a doubt, smoking a pipe. Your hair is so carefully slicked back that it sometimes sticks to the back of chairs.

You have been charged with designing the new motorway's interchange with the A405 at Bricket Wood. Until now, your career has involved designing mundane things like roundabouts and crossroads and little bypasses. Your new layout for Bricket Wood is, by comparison, rather dashing. Not only does it have two really space-age loops in it, but it's also nicely integrated with the existing road layout there, including the residential streets! Cool, daddy-o! Job done.

It's only a few years later, when you see that everyone else was designing two-lane sliproads, enormous roundabouts, and segregating fast motorway traffic from the existing street network, that you start to think that maybe you should have paid more attention to those reports about American freeway design practice that everyone else was talking about.

You quietly move away from the area and get a job designing small roundabouts in the west country.

What would be better?

It's already been substantially altered from its original design, turning the A405 into a 'longabout' rather than having T-junctions where the sliproads join it.

The real problem is that horrendous southbound sliproad. Its curve could be tightened slightly (and let's face it, it's so tight already that it would hardly matter) to a new line just alongside the part with houses and junctions, leaving the original sliproad for local traffic and a new one next to it for motorway traffic. The cut-through on the A405 just to the north of the junction could then be turned into a full crossroads with local access there to the Old Watford Road. Still not perfect, but better than this.

Routes

Right to reply

Truvelo 15 February 2009

I think this junction is marvellous. I use this junction to get from the bottom end of the M1 to the M25 and the northbound exit slip enables a freeflow route to M25 J21a with only a set of pedestrian controlled lights to half progress. A conventional roundabout or additional traffic lights would delay my progress. Ultimately M1 J6a should have had all movements provided then non of this would have been an issue.

John Morgan 15 February 2009

We were travelling north on the M1 and needed to change drivers, but for some reason didn't stop at Scratchwood services. So we turned off here, into the local housing estate!

The "longabout" on the A405 took me by surprise, and it is not well signed when you reach the bottom of the sliproad. And then that access to the housing off the southbound sliproad! Extraordinary!

By way of explanation (NOT defence!) - this style of junction was common at the time. See also M1 J9 (A5, Markyate), M2 J2, 3, 5 and 6, M20 J6 and 7 (all as originally built - some have since been rebuilt), or the various junctions on the A1 bypasses around Stamford, Grantham and Newark. Also, thinking about it, some of the junctions on the M5 between Birmingham and Worcester, again rebuilt when the M5 was widened to 3-lanes each way a few years ago now.

It seems to work quite well for quieter junctions, but is probably difficult at busier junctions - as Bricket Wood is, surely, now. This junction's other claim to fame is as the original Mr Floppy as on your links page.

Lewis 15 February 2009

Regarding the Bricket Wood bad junction - you rightly list it on your site, but I can add another very good reason for it to be here, should one be needed.

Because of the tightness of the curves, everyone has to suddenly brake to 30mph when going around them. This causes a backlog on the northbound M1, where every day without fail the inside lane on the M1 anything up to half a mile on approach grinds to halt while the other two lanes scream past.

The other is the sheer complexity of some movements on the system - from M1 Southbound to A405 Eastbound it's a grim series of crossing lanes and turning into wrong directions where your brain tells you you're going the wrong way.

And because the sliproads are so itty-bitty, there is no room for any advanced signage of the labyrinth of lanes on the A405 to let unsuspecting drivers in on the joke!

David 15 February 2009

Indeed, truly an awful junction though I do have one defence for it: it allows guilt free pedal to the metal acceleration as you join the M1 southbound.

Hal 16 November 2009

I use this junction many times... The one thing I've noticed is when traveling South on the A405 to join the M1 southbound. The A405 is 50MPH, when you turn off onto 'Mount Pleasant' the speed is reduced to 30MPH but after the local road 'turns off' there is no change of speed limit, so you join the M1 limited to 30MPH...

It should be relatively easy to link the Westbound on slip at M25 J21a and the M25 a/c slip at J21 to create a simple (and orthodox) route from A405 onto M1 Northbound. That would at least allow the M1J6 n/b slip road to be closed, and the n/b exit slip would therefore become one way (always a good idea) either with an extra lane or with the curve eased.

A similar link could also be made for traffic to exit M1 s/b at J6a, cross to the M25J21 clockwise exit slip and join A405. It would need to be designed carefully to maximise the distance between the merging of the slip roads and the A405 roundabout, though these would remain closer than optimal. However, removing the need for the sharp exit curve at M1J6s/b would allow a re-alignment of the M1J6s/b on slip and common-sense separation of local and motorway traffic.

Tobye 25 February 2016

Using this junction at least 4 times a week, I don't think I've ever managed to join the M1 South doing more than 25mph, it's a very scary situation joining a motorway at less than 45mph. This is possibly the worst and most under-capacity motorway junction I've ever encountered! Something needs to be done, access to Watford is a nightmare with this ghastly mess!

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