Pointlessly Dangerous road designs that should be removed.

[Joe_Flyover]

Recently a junction not far from me played host to a tragic death...

http://www.cambridge-news.co.uk/Newmark ... 174156.htm

While if taken at appropriate speed it should be possible to negotiate it safely, the design nonetheless seems to incorporate needlessly sharp turns, a far more direct on-slip would have been built easily. And though a side issue, takes up a large amount of land, again, pointlessly.

https://maps.google.co.uk/maps?q=A1304, ... m&t=h&z=16

Why would they build it like this? (the slip from the a1304 to A11) I was thinking there is a racehorse crossing there and maybe the slip would have sharp turns to slow traffic, but the off-slip would be more important for this and yet is straight, allowing for high speeds.

[echowarning]

I'd assume land take is the issue, as well as bridge length - if you wanted A1304 to A11 without the curve, you'd be bridging a significant distance.

The A1304 is S2 and therefore has a design speed of 60mph for that corner I'd assume - the A11 and A14 are the main routes and carry the majority of traffic and therefore are built to a higher standard.

I'm guessing - but nothing about this junction looks at all dangerous to me.

[Johnathan404]

The problem with that junction is that it's over-built. Sweeping bends on an empty road are good fun, but how much time does it save over something much slower?

Having said that, it also looks like the cheapest solution for that junction.

[echowarning]

The problem with that junction is that it's over-built. Sweeping bends on an empty road are good fun, but how much time does it save over something much slower?

Having said that, it also looks like the cheapest solution for that junction.

Well yes, quite.

The A14 here is busy at times, but generally nothing like the mess over the other side of Cambridge - and the A11 itself is hardly busy either. Free-flow to the A1304 does seem like massive over-engineering.

Still, better this than a cheeky roundabout for A1304 / A11 with slips to the A14!

[Truvelo]

Junctions in America, where the driver involved came from, often have worse curvatures than over here so he should be used to negotiating such bends.

As for the junction, it's a nice example of a freeflow design of its time. Today it would just be a roundabout or dumbbell.

[Derek]

I suspect the reason it was built like this is historical.

When the Newmarket bypass was built the A11 turn off ended abruptly on the old All at the top of the hill where the two carriageways come together, north of here wasn't dueled for many years. Point being if the A1304 had to join the A11 before the merge it had to do so far enough back to avoid serious weaving problems.

Have to say though I've driven this several times and in all honesty it's a very well designed junction if you take it at an appropriate speed.

Derek

[wrinkly]

Don't know if this is relevant but the two junctions on the Newmarket bypass between the A11 and what is now the A14 were originally going to give priority to the A11 and were changed during the design phase.

[Debaser]

I'd go with bridge length and skew angle. Ideally you want a bridge to be perpendicular to the carriageway it crosses so as to be as short (and therefore as cheap) as possible. Unfortunately, that means that when you put on your minimum curve radii to keep land-take to a minimum, they still take up a fair amount of land. The alternative is a large skew leading to perhaps larger, shallower radii, making the structure more expensive.

[ajuk]

Not only is it over built, but the range of movements looks quite limited.

[Helvellyn]

Not only is it over built, but the range of movements looks quite limited.

The only one that seems to be missing that might matter is the A14 west to the A11. A14 west to the A1304 looks like it's well enough catered for by the previous junction and the B1506 (works in both directions actually), even if it means going through a village, and I can't see there being much desire for the other missing ones.

[DavidNW9]

This is the first I ever saw of what is now an epidemic. They present a potential fatal accident every time they are used as someone will always chance it to get through before a car is coming the other way. I assume it's from councils who want people to get off the roads, although of course it's not just car drivers who are forced to suffer, just like with humps, this is a bus route and emergency vehicles report many major problems caused by negotiating such atrocities.

http://goo.gl/maps/7s9OD

[echowarning]

This is the first I ever saw of what is now an epidemic. They present a potential fatal accident every time they are used as someone will always chance it to get through before a car is coming the other way. I assume it's from councils who want people to get off the roads, although of course it's not just car drivers who are forced to suffer, just like with humps, this is a bus route and emergency vehicles report many major problems caused by negotiating such atrocities.

http://goo.gl/maps/7s9OD

These things are in 20/30 limits through, right?

A driver that 'chances it' on one of these would've no doubt been going even faster if the traffic calming wasn't there...

[Debaser]

I assume it's from councils who want people to get off the roads, although of course it's not just car drivers who are forced to suffer, just like with humps, this is a bus route and emergency vehicles report many major problems caused by negotiating such atrocities.

http://goo.gl/maps/7s9OD

And if you rotate the view 180 degrees there's a school entrance. Given the geometry of that road I wouldn't trust some drivers not to exceed the limit even at school start and finish times and with parked cars.
http://goo.gl/maps/nnaqg

The build out might not be ideal, but it creates a gateway into an area where kids will be crossing at random on an otherwise featureless road. On the other side of the entrance, this road being the minor arm of a T-junction, one would hope drivers entry speeds would be low and remain relatively low as they get to the school, so nothing appears to be needed.



E.T.A. The build out also seems to be on a ped desire line, so it's also bringing peds directly into the vision of drivers and reducing their crossing time.

[RJDG14]

I've got two solutions - Either build a grade seperated roundabout or reduce the curve (The second would also do good for the farmers).

[M19]

I assume it's from councils who want people to get off the roads, although of course it's not just car drivers who are forced to suffer, just like with humps, this is a bus route and emergency vehicles report many major problems caused by negotiating such atrocities.

http://goo.gl/maps/7s9OD

And if you rotate the view 180 degrees there's a school entrance. Given the geometry of that road I wouldn't trust some drivers not to exceed the limit even at school start and finish times and with parked cars.
http://goo.gl/maps/nnaqg

The build out might not be ideal, but it creates a gateway into an area where kids will be crossing at random on an otherwise featureless road. On the other side of the entrance, this road being the minor arm of a T-junction, one would hope drivers entry speeds would be low and remain relatively low as they get to the school, so nothing appears to be needed.



E.T.A. The build out also seems to be on a ped desire line, so it's also bringing peds directly into the vision of drivers and reducing their crossing time.

That is a rare build out that seems to have been designed to be part of the road. In other words not one of those nasty retrofitted triangle of kerbs filled with a some leftover tarmac, which engineers, for some reason love to use.

[M19]

Not only is it over built, but the range of movements looks quite limited.

Its a classic 70's design that I quite like - simple and functional.

It could have been a lot worse - a inconvenient dumbell with overtight new-age lorry toppling roundabouts, used not for this type of arrangement but also inappropriately for tieing in just about any road regardless of whether its a minor road or a major dual.

The way standards have been watered down we'll be going back to T-junctions next between major A roads and motorways.

[Keiji]

Why would they build it like this? (the slip from the a1304 to A11) I was thinking there is a racehorse crossing there and maybe the slip would have sharp turns to slow traffic, but the off-slip would be more important for this and yet is straight, allowing for high speeds.

That junction looks fine in terms of layout. All it needs is an ADVISORY speed limit appropriate for the bend, sharp deviation (chevron) signs, and possibly a reduction down to one lane since the approaching road is one lane anyway.

[Haydn1971]

Going back to basics - what happened in the accident ?

The slips look very capable of being driven well in excess of the speed limit - but I'd question the appropriateness of the priority junction as the slips join the A1304

Otherwise, can I ask why Joe feels the junction is dangerous ?

[nowster]

I'm in agreement with Haydn here. From GSV, it looks a very easy bend, and I'd need to know more of the circumstances (which the news article is light on) before making any judgement.

[ajuk]

Hayes Way/ A38, where to start. There's traffic interacting that doesn't even need to interact.