More Freeflow in One Direction.

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SteveA30
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More Freeflow in One Direction.

Post by SteveA30 »

Which routes are more freeflow in one direction than the other?

Heading west along M25/A3/A31,
M25-A3 is a freeflow left if you get the lights just right.

A3-A31 is an off-slip, whereas e/bnd is tricky due to heavy A3 traffic, causing AM rush hour queues along the entire Hogs Back.
A31 at Shepherd and Flock, is a freeflow lane, whereas east has 1 set of lights.
A31 at the end of the Alresford bypass rbt, is a freeflow lane onto the D2, whereas east is a normal rbt.
A31-M3 has 2 normal rbts but, east has 1 signalised rbt, plus the other 2.
Last edited by SteveA30 on Mon Mar 28, 2016 07:53, edited 1 time in total.
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Piatkow
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Re: Freeflow in One Direction.

Post by Piatkow »

A417 as a freeflow lane avoiding Zoons Court Roundabout travelling towards the M5 and Birdlip.
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Re: Freeflow in One Direction.

Post by Andy33gmail »

I believe this, or something similar, was a question in one of the most recent pointless quizzes, so should be a few there
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Re: More Freeflow in One Direction.

Post by crb11 »

A4008 in Watford from M1 J5 to the Bushey roundabout bypasses two of the three roundabouts and has a much easier path through the one-way system than the reverse.
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Brenley Corner
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Re: More Freeflow in One Direction.

Post by Brenley Corner »

A229 Southbound onto M20 eastbound is a painted left-turn freeflow lane, but going the other way involves a 270 degree bend on the slip road, left turn onto a roundabout under the M20, and then cross another roundabout before merging onto the A229.

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jackal
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Re: More Freeflow in One Direction.

Post by jackal »

There must be hundreds of left-turn filters at roundabouts and related junctions that would meet the criterion of 'more freeflow in one direction than the other'. Simister Island alone has four instances of this.

The upgrade at M4-A404 (Handy Cross) has a more elaborate left turn filter with additional grade separation from a local road. The opposite movement is via the roundabout.

There are also many urban/surburban one-way flyovers, e.g. A444 leaving Coventry or A52 leaving Derby. Chiswick flyover may be the best known example.

Lots of trumpets have an at-grade junction after the left turns, meaning the left turns freeflow but the right turns don't - here's an example.

Finally, non-standard grade-separated designs often provide more freeflow in one direction than another - for instance, M5/A417 or A52/A453.
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Re: More Freeflow in One Direction.

Post by Jeni »

Heading from the M56 to M6 on the A556, westbound has a freeflow left turn at both roundabouts, while eastbound has to go all the way round each one.
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Re: More Freeflow in One Direction.

Post by Fahad »

SteveA30 wrote:M25-A3 is a freeflow left if you get the lights just right.
How are we defining freeflow here?

I'd understand the term to mean that while traffic making this movement might have to make an equal-priority merge or a tiger tail merge; it could not pass through traffic lights or ever have to give way to another flow. I think you're referring just to whether traffic can make the movement at speed, which while relevant to individual users isn't to the flow as a whole
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Re: More Freeflow in One Direction.

Post by SteveA30 »

No, I just added that one to make the whole A3/A31 route sound better. I do mean freeflow lanes without lights.

Another example is the A4042, where there are 2 freeflow rbts southbound. I'm sure there was a third but, Google don't show that.
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Re: More Freeflow in One Direction.

Post by trickstat »

jackal wrote:There must be hundreds of left-turn filters at roundabouts and related junctions that would meet the criterion of 'more freeflow in one direction than the other'.
A good example is the A12/A406 Redbridge Roundabout. Heading east on the A12 and then turning north onto the A406 there is a filter lane which, even at quite busy times, tends to involve little more than a bit of being wary of traffic filtering in from the previous junction. In the opposite direction, the queue for the roundabout often stretches several traffic light changes back and gets close to the A406/M11 junction and then you may also get caught by the other lights on the roundabout itself.
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OLD GIT
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Re: More Freeflow in One Direction.

Post by OLD GIT »

Free flow in one direction- I thought that was a concept best suited to traffic flowing INTO Merseyside ,from the rest of the UK. :shock:
Meant as a comical suggestion that folks travel out on train, and back in in cars :D
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the cheesecake man
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Re: More Freeflow in One Direction.

Post by the cheesecake man »

OLD GIT wrote: Wed Mar 30, 2016 22:05 Free flow in one direction- I thought that was a concept best suited to traffic flowing INTO Merseyside ,from the rest of the UK. :shock:
Meant as a comical suggestion that folks travel out on train, and back in in cars :D
Or do folks travel in by car then out by train due to car being nicked/ burnt out/ stripped of tyres/ [insert preferred unfair Merseyside stereotype here]? :stir:

There's a one-way flyover from the A630 to the start of the A18 in Doncaster.

I encountered one at Salt End on the A1033.

In both cases other movements use the roundabout.
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c2R
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Re: More Freeflow in One Direction.

Post by c2R »

the cheesecake man wrote: Thu Aug 06, 2020 18:56

I encountered one at Salt End on the A1033.

In both cases other movements use the roundabout.
If you think about what direction freight is going at this one, it wouldn't make sense to grade separate traffic in the other direction only - However, I've never been sure as to why the flyover wasn't made an S2, as the AADT travelling across it can't be that high....
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Re: More Freeflow in One Direction.

Post by jervi »

I'd say the A23(T) - A27(T)
Only A27 EB - A23 NB has a full free-flowing NSL link. All other connections use a 50mph spur, and run through either 1,2 or 3 roundabouts. Although the A23 SB to A27 WB (opposite from the freeflow) are segregated from the roundabouts and such are technically free flow since they don't give way to anything. Although on all documentation I've seen it says the junction only has 1 free flow movement.
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the cheesecake man
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Re: More Freeflow in One Direction.

Post by the cheesecake man »

c2R wrote: Thu Aug 06, 2020 18:59
the cheesecake man wrote: Thu Aug 06, 2020 18:56

I encountered one at Salt End on the A1033.

In both cases other movements use the roundabout.
If you think about what direction freight is going at this one, it wouldn't make sense to grade separate traffic in the other direction only - However, I've never been sure as to why the flyover wasn't made an S2, as the AADT travelling across it can't be that high....
I'd expect more freight leaving and joining the A1033 (to and from the massive chemical works south of the road at that point and the industrial area to the north) than staying on it (to and from the fairly empty rural area to the east)? The biggest freight movement out of Hull is caravans so there'll be more heading east from Hull towards the coast than the other way. That could be why it wasn't an S2 (ie wide caravan heading east meeting big lorry heading west on flyover = crunch).
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c2R
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Re: More Freeflow in One Direction.

Post by c2R »

the cheesecake man wrote: Thu Aug 06, 2020 19:23
c2R wrote: Thu Aug 06, 2020 18:59
the cheesecake man wrote: Thu Aug 06, 2020 18:56

I encountered one at Salt End on the A1033.

In both cases other movements use the roundabout.
If you think about what direction freight is going at this one, it wouldn't make sense to grade separate traffic in the other direction only - However, I've never been sure as to why the flyover wasn't made an S2, as the AADT travelling across it can't be that high....
I'd expect more freight leaving and joining the A1033 (to and from the massive chemical works south of the road at that point and the industrial area to the north) than staying on it (to and from the fairly empty rural area to the east)? The biggest freight movement out of Hull is caravans so there'll be more heading east from Hull towards the coast than the other way. That could be why it wasn't an S2 (ie wide caravan heading east meeting big lorry heading west on flyover = crunch).

Yeah, so the freight leaving the A63/A1033 is separated from the oncoming traffic, and is able to turn without impeding the flow of traffic coming the other way, as this is the major conflict - if the viaduct was one way in the opposite direction, the main conflict would still exist. I suspect that they didn't want to separate the traffic in with a curved viaduct as it would likely cause other issues.

As for S2 flyovers, the A47 at Hardwick seems to manage, also despite caravans and high freight volumes...
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Re: More Freeflow in One Direction.

Post by Stevie D »

c2R wrote: Thu Aug 06, 2020 18:59
the cheesecake man wrote: Thu Aug 06, 2020 18:56I encountered one at Salt End on the A1033.

In both cases other movements use the roundabout.
If you think about what direction freight is going at this one, it wouldn't make sense to grade separate traffic in the other direction only - However, I've never been sure as to why the flyover wasn't made an S2, as the AADT travelling across it can't be that high....
My guess would be that there is a lot of traffic heavy turning between Hull and the old refinery. That would mean that without the flyover, traffic coming from Hull and turning into the refinery would cross the path of traffic coming from Hedon towards Hull. By having the flyover as inbound, it removes that conflict, whereas outbound wouldn't have the same impact.
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jackal
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Re: More Freeflow in One Direction.

Post by jackal »

It is very common of course to have a freeflow left turn at a roundabout or other at-grade junction, and even somewhat common to have a one-directional flyover of an at-grade junction (e.g. A52 approaching Derby, A18/A630 Doncaster).

What's quite unusual, for obvious reasons, is freeflow for the right turn of a pair of movements, but not the (typically easier) left turn. There's a quite spectacular double example on the proposed LTC/A13 interchange, where A1079 to LTC northbound and A1079 to LTC southbound are possible but the reverse movements aren't:

A13 LTC 2020 - Copy.jpg

This is partly explained by M25 clockwise to A13 eastbound being freeflow at M25 J30.
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Re: More Freeflow in One Direction.

Post by Big L »

One-way flyover at the Pentagon roundabout in Derby isn't there?
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