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Crace Roundabout

By grumpyrhonda 28 October 2010 55

What is the go with Crace roundabout?  A single lane approaches a roundabout then it becomes two lanes to facilitate the movement of traffic and then merges back into one lane.

At Crace roundabout, heading toward the Barton Highway, drivers seem to have the moronic idea that they are meant to queue on the outside lane all the way back to bloody Palmerston.  God help you if you have the temerity to actually use the inside lane of the roundabout as it’s intended.

You have the morons in the outside lane fuming at you for using the inside lane when it’s acceptable to do so.  I’m looking forward to other rioters comments on this.  I’m sure I will be blasted.


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Crace Roundabout
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Erg0 12:25 pm 02 Nov 10

clueless70: It sounds to me like the people you’re describing in your first example are actually breaking the law by going straight from a left turn only lane, which is a totally different discussion than the one we’re having here.

shadow boxer 11:53 am 02 Nov 10

I prefer to think of them as chicanes, excellent passing opportunities if you get the timing right.

montana 11:43 am 02 Nov 10

ah single lane roads with double lande roundabouts?

these personally are my favorite overtaking opportunities especially if there is a slow car infront of me, and no overtaking lanes is available for a while.

overtaking could potentially same me minutes.

havent really encoutered these in peak hour traffic though so not sure if it would save me time in that situation.

DJ 10:23 pm 29 Oct 10

I enjoy reading about Canberra drivers this and Canberra drivers that… oddly, you are all driving in Canberra doing the same things to each other. I don’t understand how we all can recognise the congestion and yet still get caught up in it all the time. I bet nobody here would put their hand up and admit that they are not perfect drivers.

clueless70 9:41 pm 29 Oct 10

You aren’t solving the problem utilizing that lane. You ARE the problem.

I’m with you there Mothy. In one 4-way intersection near my house was a small puzzle of game theory that repeatedly confounded most players because its solution was non-intuitive. Two opposing pieces of roadway each spawned a left-hand turning lane on the approach and narrowed back to one lane on the other side of traffic lights. Queues formed because some drivers from either approach always wanted to turn right, and their turning sometimes hindered those who were passing straight through. As the queues grew, the lure of the left-hand turning lanes would become irresistable to some drivers who peeled off left, ‘undertook’ the queue, and by swerving twice across marked lines crossed the intersection NOW instead of waiting their turn. They would then run out of space as the road narrowed to its usual one lane, impeding one another, of course, and dangerously barging back into the stream of cars crossing straight through which was reluctant to receive them. But the impatient drivers also prevented the right-turners from completing their perfectly legal turns when, if it weren’t for the queue-jumpers, a gap might have appeared in the through-traffic for such a turn. This led to queuing, and so the lure of the left-hand turning lanes would become irresistable etc etc.

There is a variation that only requires one side of a dual carriageway.
On the road I drive at, or sometimes slightly above or even slightly below (since I am not a robot) the posted speed limits. This places me in opposition to the 60 to 70 percent of drivers who, for unclear reasons, constantly exceed posted speed limits. More than once I have completed overtaking a driver who is driving at a good deal less than the posted limit. For a moment this places me in the outer lane, where I know better than to linger. But before my hand reaches the indicator to indicate my return to the inside lane, three or more following drivers in the majority group mentioned aggressively ‘undertake’ me at speeds well above the posted speed limit, preventing me from leaving the outside lane for as long as they consider me to be leaving this lane too slowly. It can be quite a long time before those who did not want to be on the inside lane have finished their undertaking of me there, so that the way is clear for me to leave the outside lane where I do not want to be.

In each case the queue-jumpers are sustaining and adding to the queue itself. Self-interest is the solution – unless it is the problem.

Holden Caulfield 8:59 pm 29 Oct 10

Groan.

I tried, haha!

Mothy 5:15 pm 29 Oct 10

BenMac said :

Both the left and right hand lanes can continue down the GDE. There isn’t a sign that says Left Lane City, Right Lane GDE. I don’t see the problem. The lane is there to be used. I find it stupid to see 50 cars in a line with a free lane next to them. Am I going to be car 51, or use the free lane as intended? No points for guessing.

Follow this logic through Ben. Assume everyone agrees with you, and half the cars that would otherwise line up in the right lane split off and use the left lane.

Now, instead of one line of 50 cars, you have two lanes of 25 cars, and the need to juggle a merge.

Net time saved = Nil.

AND

For anyone turning left heading towards the city via Barton Highway, you’ve just introduced a line to their lane of traffic that didn’t need to be there.

Yeah, I can see how you’re really delivering some good community service there. Not.

Holden Caulfield said :

Here’s a simple scenario for the doubters that using both lanes at a roundabout could possibly improve the traffic flow. This scenario does not involve a roundabout at all, but is a simple display of traffic management. It involves an 8 lane cross intersection (ie. two lanes of traffic in each direction) controlled by a set of traffic lights.

In other words, a completely different scenario to the one under discussion, because you assume your lanes are continuous and your 30 cars can all fit in the space on the opposite side of the intersection.

If there’s only room for 15 cars, then 7.5 from each line are going to make it through the lights. Net gain for the body of traffic = Nil.

Look past the immediate please folks, particularly when driving.

Holden Caulfield 10:32 am 29 Oct 10

BenMac said :

Those of you who get angry by this need to lighten up.

Both the left and right hand lanes can continue down the GDE. There isn’t a sign that says Left Lane City, Right Lane GDE. I don’t see the problem. The lane is there to be used. I find it stupid to see 50 cars in a line with a free lane next to them. Am I going to be car 51, or use the free lane as intended? No points for guessing.

Agreed.

A perfect example of this lemming phenomenon can often be seen at traffic lights where people just line up one behind the other leaving an adjacent lane empty, or with very few cars in it.

Here’s a simple scenario for the doubters that using both lanes at a roundabout could possibly improve the traffic flow. This scenario does not involve a roundabout at all, but is a simple display of traffic management. It involves an 8 lane cross intersection (ie. two lanes of traffic in each direction) controlled by a set of traffic lights.

For the purposes of this discussion, let’s assume under normal circumstances 15 cars per lane can get through the intersection under a regular green light cycle.

If you and 29 other motorists are all driving in the left lane and you approach the traffic lights which are currently red, which of the following options do you think will flow best through the next green light cycle?

1. One line of 30 cars using the left lane only.
2. Two lines of 15 cars using both the left and right lane.

The second option works best, clearly.

I’m not for one moment suggesting that this is a foolproof scenario that applies equally to the traffic flow at roundabouts in all circumstances. It is intended to be a simplistic illustration to explain how moving as many cars through a green light cycle, or a safe gap at roundabout, can assist the flow of traffic as opposed to voluntarily restricting that flow by using one lane only.

WhyTheLongFace 5:05 am 29 Oct 10

Rollersk8r said :

Because it’s bloody rude and unecessary to use it as your own personal overtaking lane.

And, if you’d applied any logic to this, you’d realise that jumping out of line and forcing your way back in slows down the whole queue.

If you go from Ginniderra Dr out to Horse Park Dr there’s something like 9 roundabouts in a row. Aggressive a-holes therefore get 7 or 8 double-lane chances to cut you off and be 1 car ahead.

It absolutely should be a 2 lane road all the way from Barton Hwy through to Horse Park but that’s another issue…

100% correct. RUDE AS HELL!

It isn’t an overtaking lane. To use it as one is just moronic, rude and dangerous.

I found a great solution. I chose the lane that the car in front doesn’t go in (right or left doesn’t matter) and stay close, but just behind that car. Then I merge back in behind that car, back to where I was. It stops any cars behind me from trying to do any suicidal ‘Dukes of Hazzard’ overtaking.

This would so easily be solved by making one lane straight ahead only and the other a turning only lane. As it is in other capital cities around Australia.

I’ve also noticed a regular supply of broken glass at these roundabouts. I wonder how many accidents have been caused by these embarrassing roundabouts and the inconsiderate jerks who misuse them?

BigDave 11:52 pm 28 Oct 10

Canberra drivers crap at merging? No, they are crap at everything!

bd84 8:44 pm 28 Oct 10

Anyone with half a brain would realise that if traffic is slow moving bumper to bumper, that moving some of the traffic from one lane to two for 20 metres to merge back into one is not going to improve the flow of traffic whatsoever, but create more traffic problems. The vast majority of Canberrans do not understand the rules of merging, how to use an indicator or what give way means. Anyone thinking they can use the 2nd lane and try and force someone on the other side to give way in that traffic is a moron.

BenMac 6:38 pm 28 Oct 10

Vegemite said :

Mothy said :

GBT said :

While there is nothing legally wrong with doing this, it isn’t helping anyone but yourself, to the detriment of others waiting. If you think this speeds up traffic flow as a whole you are delusional.

+1

Same for the bloody left hand lane on the GDE where the traffic can exit to Barton highway, but the lane continues on for 50 meters before a “Form One Lane”.

Asshats see the queue in the right hand lane, often all the way back to the lights at Mitchell, jump in the left lane, dash down to the merge point, and shove their nose back in the queue.

Drives me crazy, gains them so little.

Oh golly!!! I have been waiting for someone to post on this exact situation. I have been trying very hard not to lose my patience with the idiots who do this on Gungahlin Drive every morning…..

Keeping in the right hand lane on Gungahlin Drive actually does serve a purpose in the mornings as it keeps the lane clear for those people who are turning on to the Barton Highway towards the city. So the people who use the left hand lane to get ahead in the long line of traffic really are a bunch of impatient ass hats who need to learn the basics of waiting in a line, respect for others and some ettiquette for your fellow citizens who are all stuck going slow!!!

Those of you who get angry by this need to lighten up.

Both the left and right hand lanes can continue down the GDE. There isn’t a sign that says Left Lane City, Right Lane GDE. I don’t see the problem. The lane is there to be used. I find it stupid to see 50 cars in a line with a free lane next to them. Am I going to be car 51, or use the free lane as intended? No points for guessing.

Grail 5:13 pm 28 Oct 10

Using two lanes to get traffic through the roundabout faster only works if the traffic is not banked up on the other side of the roundabout too.

Merging two lanes into one will reduce the rate of passage (cars passing a fixed point, per unit time) of traffic in the two lanes to about 1/3 the speed of the traffic in the single lane. Splitting one lane into two increases the rate of passage of vehicles by 2. So curiously enough, if you have a single lane that then splits into two, then merges back into one, guess what happens? That’s right! You get a net speed decrease of roughly 1/3 over exactly the same traffic staying single file.

If traffic in the single lane after the merge is travelling smoothly at 100km/h, you’ll see traffic in the double lanes travelling at about 40km/h, and traffic in the single lane before the split will be travelling smoothly at about 70km/h (to one significant digit).

So please, if the road is full of single file traffic before and after the roundabout, stay single file.

Holden Caulfield 4:57 pm 28 Oct 10

Vegemite said :

Oh golly!!! I have been waiting for someone to post on this exact situation. I have been trying very hard not to lose my patience with the idiots who do this on Gungahlin Drive every morning…..

Keeping in the right hand lane on Gungahlin Drive actually does serve a purpose in the mornings as it keeps the lane clear for those people who are turning on to the Barton Highway towards the city. So the people who use the left hand lane to get ahead in the long line of traffic really are a bunch of impatient ass hats who need to learn the basics of waiting in a line, respect for others and some ettiquette for your fellow citizens who are all stuck going slow!!!

So you have labelled others as idiots and impatient ass hats while asking for respect and etiquette from the same people you have just insulted. That’s brilliant, haha!

Mothy 4:56 pm 28 Oct 10

el said :

Except twice as many cars are able to enter and exit the roundabout each time there is a gap in traffic, so yes, it does speed up flow

Or, as is the case, there isn’t CAPACITY on the other side of the roundabout for that increased volume to pass THROUGH the roundabout – i.e. the stupid road goes back to one lane.

There is no need to wait for a “gap in the traffic” – beyond the courtesy of not queuing through across/through the intersection/roundabout – very few people come from Belconnen into Crace across the flow of traffic.

So any “gaps in the traffic” are just the opening up of space on the other side of the intersection. Getting in the left hand lane and overtaking maybe one car, just jams you into that space on the other side marginally quicker, and at the expense of the right hand lane traffic that your were, until the second lane opened up, sitting in, slowly crawling towards the roundabout, wondering why the line was moving so slow.

You aren’t solving the problem utilizing that lane. You ARE the problem.

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