Motorway Road Rage - Brits are idiots when they arrive at roadworks
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glasgowcyclist
Charming but somewhat feckless
- Location
- Scotland
swee'pea99
Legendary Member
Thinking about this in the context of a real-life scenario, in my case the three or four times a year trip down to the west country, I have many times, waiting in line to get past Stonehenge, wondered why we are all doing 2MPH rather than 30MPH.
There's a pinch point, a one-lane stretch of road through which cars go in single file at a crawl. Beyond that point, the open road, with cars immediately able to return to 50MPH or whatever. Given that the road beyond the pinchpoint is completely clear, why don't/can't all cars go through it at, say, 30MPH? The only answer I can think of is inefficient merging, which builds on itself, reinforcing the delays, and ending up with the net result: a crawling pinch point, with a big reservoir of cars backed up behind it, and a trickle coming out the other end.
I wonder if one day, when Google's driverless cars have become universal, with cars not only driving themselves independently with maximum efficiency, but communicating wirelessly in real time so that the entire 'car universe' works cooperatively to maximise efficiency, such pinch points would if not disappear (there's always going to be potential for a fundamental mismatch between the demand for any given road capacity and the amount of road capacity available) at least have their negative effects minimised, by cars merging flawlessly, like teeth in a zipper.
(Sits back and waits for somebody who understands maths/mechanics to explain a) how wrong he is, and b) how stupid he is not to see it, using logic and language he will c) fortunately be too dumb to grasp.)
There's a pinch point, a one-lane stretch of road through which cars go in single file at a crawl. Beyond that point, the open road, with cars immediately able to return to 50MPH or whatever. Given that the road beyond the pinchpoint is completely clear, why don't/can't all cars go through it at, say, 30MPH? The only answer I can think of is inefficient merging, which builds on itself, reinforcing the delays, and ending up with the net result: a crawling pinch point, with a big reservoir of cars backed up behind it, and a trickle coming out the other end.
I wonder if one day, when Google's driverless cars have become universal, with cars not only driving themselves independently with maximum efficiency, but communicating wirelessly in real time so that the entire 'car universe' works cooperatively to maximise efficiency, such pinch points would if not disappear (there's always going to be potential for a fundamental mismatch between the demand for any given road capacity and the amount of road capacity available) at least have their negative effects minimised, by cars merging flawlessly, like teeth in a zipper.
(Sits back and waits for somebody who understands maths/mechanics to explain a) how wrong he is, and b) how stupid he is not to see it, using logic and language he will c) fortunately be too dumb to grasp.)
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
Them damned yankees call it the zipper merge. And it works.
It's as good a hypothesis as any
Joey Shabadoo
My pronouns are "He", "Him" and "buggerlugs"
I now understand why the helmet thread is so huge.
CopperCyclist
Veteran
Both arguments are right in a given scenario.
If N lanes are reduced to N-1, thus that the only option is every to drive in that/those lanes, and all traffic are therefore going on the same direction, then queue in both, and merge in turn. The queue is made shorter and it is the most efficient way.
If the traffic has two options to take at the queue point (think Cubists example above of traffic queuing in Lane 1 to all exit the slip road) then you need to merge early and get into that queue so that the traffic taking the other option can flow freely.
If N lanes are reduced to N-1, thus that the only option is every to drive in that/those lanes, and all traffic are therefore going on the same direction, then queue in both, and merge in turn. The queue is made shorter and it is the most efficient way.
If the traffic has two options to take at the queue point (think Cubists example above of traffic queuing in Lane 1 to all exit the slip road) then you need to merge early and get into that queue so that the traffic taking the other option can flow freely.
Shadow
member
- Location
- edge of the south downs
That'll be a TMN to me then 3BM.
(See post # 146 - 'Zip-merging is the most efficient form of moving the vehicles thru.')
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
Sorry, you're on my ignore list so I can't read your posts.
Shadow
member
- Location
- edge of the south downs
Strange, I wasn't aware of anything i'd done to provoke this extreme reaction!
marknotgeorge
Hol den Vorschlaghammer!
- Location
- Derby.
Trouble with the second scenario is that it's not always obvious why there's a queue on the main road. Traffic in lane 1 intending to stay on the main road can get caught in the slip road queue. Conversely, traffic in lane 2 intending to take the slip road can inadvertently pass the end of the queue. The best solution is to ensure the merge point is as far up the slip road as possible to minimise queuing on the main road.
There's an example of this on my commute to work. Where I usually exit the A38 to head into Burton, the two-lane slip road bears left at the point where the traffic from the northbound side of the A38 and Rolleston comes over the bridge and joins at a Give Way line - think of the bridge as an, erm, odd shaped gyratory. You can quite clearly see on the satellite image that the intention is that both lanes of the slip road should be used for Burton, but numpties still only use one lane and cause queues on the A38. I tend to drive past them and merge around the corner. You get the occasional self-righteous gimp that straddles the white line to stop me getting past, but heigh ho. I've already saved so many car lengths of needless queuing that one fewer is neither here nor there...
The zipper merge does not however include front merging, and I suspect will therefore be dismissed, despite the fact that it works
There is a defined merging area where cars politely enter in turn, one from each lane..... well before the obstruction.
A typical system has signing some miles before and a warning that you are approaching a merge zone, then signs at the merge zone to merge.
The cars then alternate in this area so that they are already in line when the obstruction is reached.
Interestingly the merge zone has start and end points, so there is also a point in the system where it becomes an offence NOT To have merged.... one that would penalise the last minute muppets that dash to the front, fail to merge properly and cause the issues in the UK
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
Yeah it does.
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
[QUOTE 3660819, member: 259"]You are Brian Sewell and ICMFP.[/QUOTE]
He's a bit common.
He's a bit common.
