Indeed I was. That explains why the idea sounded so strange.
twhitt is talking about acsenray’s response to scabpicker. I was confused too but I don’t think they are talking about vehicles exiting the freeway but about situations where one lane is closed ahead and people get out of it early. Cars should use both lanes to the merge point. (We have signs about this in Pennsylvania too though people don’t pay attention so the lane that will be closed is the best bet for a shorter wait.)
Simple. Cars moving at 50mph need less space between each other than cars moving at 70mph. Thus more cars can fit into a given section of road.
This seems to be a better analogy for explaining why when cars get into an accident and block all the lanes, traffic comes to a stop. But I think we all understand that.
It’s not that simple, though. You’d need 40 percent more cars just to achieve the same throughput.
Huh? Cars moving at 70mph move at, well, 70 mph. That is, in fact, a full 20mph faster!
The problem is generally twofold - aggressive drivers who close gaps far too quickly, which then often inspire other, passive-aggressive drivers (far more dangerous, and much bigger assholes) to stubbornly hog the left lane. This creates large impassable blocks of slower-moving traffic where everybody is tailgating everybody else and nobody can make progress. Then the aggressive drivers start whipping out into the right lane to overtake, other aggressive drivers cut them off, or they get stuck behind another slow-moving column and force their way back to the left, sending a ripple of brake lights out behind them.
You can blame aggressive drivers all you like - although there’s nothing inherently rude about wanting to speed - but ultimately it’s the failure to yield that causes those spontaneous jams. For years I’ve never understood why people don’t move right when there’s no significant slowdown to do so - nor why people insist on preforming bumper colonoscopies when there’s nowhere to go.
Any remotely modern car can easily sustain 70+ mph on a freeway, perfectly safely, until some pitworthy douche decides to play traffic vigilante. If you’re honestly traveling the posted speed limit, and it isn’t rush hour, you belong to the far right. Anyone who thinks they can travel in the left lane (which, regardless of the written law, really is the fast lane here in the western states) at the posted limit is a douchebag.
It doesn’t need to be an accident, though. Believe it or not, it can be caused by one guy tapping his brakes.
Yes, precisely. 40 per cent more cars can travel* on the same road at 50mph, without congestion developing, than if they’re going at 70.
*or, strictly, can be travelling on a given stretch of road at any one point in time. There’s a constant input at one end and output at the other. Yes, each individual car will take a greater amount of time to reach its destination, but as long as they can do it at a predictable 50mph, that’s not congestion.
And why can’t they do it at a predictable 70 mph? You seem to be suggesting that traveling more slowly will reduce traffic? 
They can’t do it at 70mph if they’re at the road’s capacity for 50mph, i.e. every driver has the minimum appropriate distance between them and the car in front. Increase the speed to 70, and you need more space between each car.
I’m not suggesting that it reduces traffic, I’m saying that it increases the number of cars which can fit on the road. (Not suggesting, but stating a proven fact. Edit: here’s a sample cite (PDF).)
That’s really just begging the question, and it’s not that simple anyway. As the number of cars goes to zero, the throughput obviously goes to zero. As the number of cars increases, you eventually get bumper to bumper with no one moving, and you again get zero throughput. So it’s not a linear relation, and there’s some optimal speed.
According to Maximum throughput in LA freeways occurs at 60 mph (PDF, and yes, that’s really the title), “Maximum throughput occurs between 50 and 70 mph in 85 percent of all 3,363 loop detectors in Los Angeles and Ventura Counties”
I don’t have time to read the whole article right now, but I suspect the explanation flex727 was asking for might be in there.
Also, FYI for everyone, there’s a free downloadable traffic simulator available.
ETA:
The important quantity is either throughput or how long it takes someone to get where they’re going, not how many cars we can fit onto the freeway.
That article seems to be answering a different question, which is 'with a normal highway speed limit posted, what average speed of vehicles offers the greatest throughput. The point of a variable limit is where the roads which have dropped well below the 50mph average vehicle speed mark. The important bit is average - we all know that a road with that kind of traffic is going to see cars accelerating from 30 to 70 then slowing back down again.
(Yes, my description using minimum distances between cars was massively simplified, but the basic concept is still there.)
Edit:
[quote]
You’re right, I suppose I was trying to evade the false assumption which sometimes crops up that higher throughput equates to faster journey times.
There seem to be a small number of aberrant people who apparently want to sit in the left land and simply match the speed of a car in the right lane. Leaving that aside as unexplainable, it makes little sense in terms of efficiency and safety to require every car to shift back into the right lane every time. If the roads are clear, drive in the left lane, have fun. I see absolutely no problem with it. For the guy coming up 20 m.p.h. over the speed everyone else is going, I’m satisfied that he can slow down a little bit and wait for the guy to temporarily shift into the right lane to let him by. There’s absolutely no reason to be on the highway and expect never to have to slow down ever for other users.
Look, we have a certain allocation of space to roads, and we have a certain number of cars using those roads. In most populated places, it simply makes no sense to reserve a limited resource simply for those drivers who want to go slightly faster than others.
It makes no sense to travel in the left lane. If you’re not actively overtaking someone (which you should be doing), and you’re not pacing someone beside you (which you shouldn’t be doing), then there is no reason to be in the left lane. Why do you want to be there? We drive on the right in America. Multi-lane highways don’t change this, they just provide a temporary solution to getting around someone without getting “MACK” imprinted backwards on your forehead.
I’m not buying this analogy at all since cars on a highway, unlike marbles in a funnel, are essentially frictionless with respect to each other (though there are forces at play, admittedly).
Furthermore, doesn’t congestion itself reduce the speed of all the vehicles on the road? Wouldn’t that make the problem self limiting?
As I see it, if there are X number of cars wanting to get from A to B on a road with a capacity of less than X, then some or all of the cars will have to wait. We can either have all of the cars on the road moving slower due to congestion, or we can have some of the cars moving somewhat faster (your scenario) with many more stopped and waiting in line to get on the road. Your scenario was tried on Central expressway in Dallas many years ago, but failed miserably. Traffic lights were installed at every entrance ramp, trying to control the traffic entering the freeway. They didn’t last long.
I’m developing a theory about this. Being from the semiconductor industry, I find that traffic on a freeway can sometimes be analogous to electron flow through a semiconductor. We’re all familiar with the ordinary concept of electrons flowing through a conductor when you have DC current flow, well in semiconductors, current flows as holes move in the opposite direction. I see the same phenomenon on congested freeways. That speedup and slowdown you see is a hole passing you by in the opposite direction. As you enter the hole, you can speed up until you catch the car at the opposite edge of the hole, then you return to your lower speed. That hole will continue behind you in the opposite direction to traffic flow. I’m not yet sure what direct application this theory would have, but look for it next time you’re on a congested freeway and see if you don’t see it too.
Because I don’t want to be changing lanes every 30 seconds. It’s inefficient and increases risk and congestion. The lane is a resource available for use. There’s no reason to leave it empty.
This is gibberish.
You’re seeing the capacity as a fixed number. It’s not, it varies depending on the speed of the traffic.
See my link for successful use of variable speed limits to reduce congestion.
Read.
Don’t put words in my mouth. How did you get from “my scenario” to metered ramps? If “my scenario” is anything, it’s for people to relax, stop cutting each other off, stay out of the left lane unless you’re actively overtaking someone, stop tailgaiting, stop tapping your brakes for no reason, and stop driving with your dick.
And by the way, Arizona and California both have metered ramps and have had them for a long time and seen success with them.
Traffic waves - http://trafficwaves.org/
Edit: damn you, Cisco.
So in other words - what I’m getting from the sum of your posts in this thread - is that you’re a left lane slowpoke and rather than do the unbelievably simple and logical thing of cutting it out now that it’s been pointed out to you why that behavior sucks, your ego makes you want to defend your senseless actions. Correct me if I’m wrong.