Bottlenecks

[Leon]

Why do bottlenecks happen?

I'm thinking specifically of two locations:
the A23 on Hnadcross hill and the Gatwick exit (N/bound) M23

In the first, you've got a 3 lane that goes into a 2 lane. about 500 yards+ later (when the traffic is fully integrated) there are a series of bends.
Usually, once I've integrated into the 2 stream, I'm still moving. Then, at the head of the bends, I'll grind to a complete halt. Why? There are no obstructions, lane closures etc

Gatwick South. OK, I can understand that the slow lane backs up with ppl leaving the M/way, fair enough. THe middle lane has a few ppl cutting across, so that's slow. But why am I sometimes caught in the fast lane at a standstill?

[Johnny]

Its simple physics

Take a hose pipe, attach it to a tap and turn it on. ... The water happily flows out.

Now squeeze the end of the pipe ......... for the water to keep coming out it must accelerate through the restriction so the flow remains the same.

Now lets look at road works ......... flow of traffic, close one lane ... AND impose a 40 mph limit ..... of course there will be a bottle neck ... the only way to keep the traffic moving is to INCREASE the speed limit through roadworks.

So I vote for 90mph limits in roadworks ..... it works for physics, so it should work for us :wack:

[Leon]

Its simple physics

Take a hose pipe, attach it to a tap and turn it on. ... The water happily flows out.

Now squeeze the end of the pipe ......... for the water to keep coming out it must accelerate through the restriction so the flow remains the same.

Now lets look at road works ......... flow of traffic, close one lane ... AND impose a 40 mph limit ..... of course there will be a bottle neck ... the only way to keep the traffic moving is to INCREASE the speed limit through roadworks.

So I vote for 90mph limits in roadworks ..... it works for physics, so it should work for us :wack:

but the point is that in the above two situations, there are NO roadworks!!!!

[PulsatingStar]

As I know this road, I will answer.

The first you mention, 3 lanes into 2, is obvious as cars have to merge, and is also close to back up onto the hill.

The 2nd, is largely due to peoples inabilty to negotiate that S bend at speed and have poo cars or trucks that cant accelerate up the other side.

Basically theres always someone in a diesel fiesta who wants to be in lane 2 going through the S at 40 mph. Next person slows down, and probably over brakes too. The person behind will do the same, then someone will change lanes and its going to cause the traffic.

I wouldnt mind, but that bend can be rounded easily into 3 figures so I hate people slowing!

Lee

[Leon]

Basically theres always someone in a diesel fiesta who wants to be in lane 2 going through the S at 40 mph. Next person slows down, and probably over brakes too. The person behind will do the same, then someone will change lanes and its going to cause the traffic.

Lee

that's what i was thinking.
It's the overbraking that seems to be the problem - but I still marvel that with a traffic stream headed by someone at 40mph that not so far back, the line will be handbrake-on stationary

[ATrull]

Basically theres always someone in a diesel fiesta who wants to be in lane 2 going through the S at 40 mph. Next person slows down, and probably over brakes too. The person behind will do the same, then someone will change lanes and its going to cause the traffic.


Isn't that the fecking truth.

[Johnny]

but the point is that in the above two situations, there are NO roadworks!!!!

It doesnt matter though ..... if you are taking the flow from 3 lanes to 2 you must increase the speed of the traffic to maintain the same flow through the restriction.

So I propose 80mph limit on motorways, 90mph on dual carriageways and 2 lane motorways and 100mph on single carriage ways ............ it would stop bottle necks overnight !

[RohanC]

Traffic managment should be part of the driving test IMO.

I saw a proggie ages ago, stating how simple changes to driving habits would reduce traffic jams significatly.

Tailgating also causes a major problem, becuase of the over braking stating above. Iam sure weve all witnessed the cascading of brakelights from the cars in front of you, sometimes goes on for ever!

Problem is peoples ignorance to other users of the road. Everone drives to get where they want ASAP. Silly thing is if people took more notice to the bigger picture, everyone would get where they want to quicker :rolleyes:

[Angry Paul]

that's what i was thinking.
It's the overbraking that seems to be the problem - but I still marvel that with a traffic stream headed by someone at 40mph that not so far back, the line will be handbrake-on stationary

High level brake lights have a lot to answer for...

People tend to see a brake light come up a few hundreds yards away and automatically seem to bring their foot onto their own brake pedal, just enough to bring the brake lights on without actually engaging any braking effect. (How many times have you followed someone in a queue and the brake lights are ablaze and you've only lifted off and you're not actually gaining one them?) This problem then goes back through the queue until people actually do start braking because they see so many red lights ahead and everyone slows down to a standstill eventaully...

[ATrull]

Traffic managment should be part of the driving test IMO.

I saw a proggie ages ago, stating how simple changes to driving habits would reduce traffic jams significatly.

Tailgating also causes a major problem, becuase of the over braking stating above. Iam sure weve all witnessed the cascading of brakelights from the cars in front of you, sometimes goes on for ever!

Problem is peoples ignorance to other users of the road. Everone drives to get where they want ASAP. Silly thing is if people took more notice to the bigger picture, everyone would get where they want to quicker :rolleyes:
For instance, if I'm in start/stop traffic I leave a 4-6 car gap infront of myself and stick it in first and take my foot off the accelerator

that way the twats in front can keep going from 0-20mph-0mph every 60 seconds, but I'll remain at a steady pace and nobody behind me will need to stop. I then switch to 2nd gear if the gap gets any larger.

[PulsatingStar]

Traffic managment should be part of the driving test IMO.

I saw a proggie ages ago, stating how simple changes to driving habits would reduce traffic jams significatly.

Tailgating also causes a major problem, becuase of the over braking stating above. Iam sure weve all witnessed the cascading of brakelights from the cars in front of you, sometimes goes on for ever!

Problem is peoples ignorance to other users of the road. Everone drives to get where they want ASAP. Silly thing is if people took more notice to the bigger picture, everyone would get where they want to quicker :rolleyes:

Yeah and no-one moves over all waiting for the driver in front to move over and so on. Obviously theres always someone holding things up at the front of the queue, but on a busy M25 that person is you ;)

Busy motorways often seem just as quick in lane one (which is where EVERYONE should be unless overtaking). Gets right on my tits when people say "fast lane". Its a fecking overtaking lane you fool.

[Leon]

For instance, if I'm in start/stop traffic I leave a 4-6 car gap infront of myself and stick it in first and take my foot off the accelerator

that way the twats in front can keep going from 0-20mph-0mph every 60 seconds, but I'll remain at a steady pace and nobody behind me will need to stop. I then switch to 2nd gear if the gap gets any larger.

I would do this, but I then get my 4-6 gap chooped to a 1 car gap by all those in the other lane steaming in and therefore pushing me further back in the traffic queue :mad:

and i'm guilty of touching the brakes when i see the lights go on ahead of me. It's a safety thing I think to make sure that the to55er behind me doesn't miss out on the fact that everyone is slowing down and slams into me. IIRC I was told to do that when learning to drive...

[ATrull]

I would do this, but I then get my 4-6 gap chooped to a 1 car gap by all those in the other lane steaming in and therefore pushing me further back in the traffic queue :mad:

and i'm guilty of touching the brakes when i see the lights go on ahead of me. It's a safety thing I think to make sure that the to55er behind me doesn't miss out on the fact that everyone is slowing down and slams into me. IIRC I was told to do that when learning to drive...

Never had that problem on motorways, oddly enough. Usualy because there isn't enough space in the other lanes to manouver out of them :D

(I joke!)

But seriously, even if people move into the gap I've made, I just treat them as the next car instead. of the one that was originaly at the other end of the gap. works for me. :) Creating a gap is really easy, too.. you just have to sit still for a minute and then go. I just ignore the traffic behind me because frankly, they aren't going to get there any faster regardless of my behaviour - I'm just going to make it more pleasant for them in the long run.

[PulsatingStar]

I would do this, but I then get my 4-6 gap chooped to a 1 car gap by all those in the other lane steaming in and therefore pushing me further back in the traffic queue :mad:


And its these people that create the traffic with constant swapping around making people react due to their actions.

A lot of people dont care though, and if you try to keep space someone will take the piss and make you lose it anyway.