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Yes, it really is the old person driving slowly.
October 26, 2010 6:33 AM   Subscribe

Wondering why the traffic is so slow? WONDER NO MORE! [Via]
posted by Lord_Pall (65 comments total) 30 users marked this as a favorite

 
So after playing with this, it appears that the problem is, as suspected, other drivers.
posted by Old'n'Busted at 6:40 AM on October 26, 2010 [4 favorites]


Well, if you want to see more traffic related software go here: nexus Disclaimer, I know the guy.
posted by jadepearl at 6:43 AM on October 26, 2010


I'll be sure to yell about this on my drive to work, when I'm stuck in traffic thanks to a lane closure. "Your politeness factor is too low, jackass!!!!!"
posted by inmediasres at 6:52 AM on October 26, 2010


I remember this from the first time it hit Metafilter. I think about it every time I'm stuck behind a truck trying to pass another truck uphill.
posted by Jugwine at 6:54 AM on October 26, 2010


I think about it every time I'm stuck behind a truck trying to pass another truck uphill.

Unsurprisingly, the Germans have a word for that.
posted by uncleozzy at 7:03 AM on October 26, 2010 [6 favorites]


Wondering why it's so perturbing?

Apply Perturbation!
posted by pracowity at 7:03 AM on October 26, 2010 [2 favorites]


I remember the 1998 version, courtesy of Mefi's own Bill Beaty.
posted by Tube at 7:09 AM on October 26, 2010 [2 favorites]


I disagree with the lane closure scenario. Trucks do not just drive up to the closed lane and stop for long periods of time. They merge first, but if nobody lets them in, they fucking squeeze in whether you like it or not.

As they should; that's what I would do. The simulation doesn't show that, though.

I'd also like to see a lane closure scenario that compared the overall effect of two strategies. 1) everyone stays in both lanes and merges at the last possible second. 2) everyone politely moves over as soon as the closure is announced, leaving a long slow-moving queue in the 'good' lane, and a long stretch of the closed lane unused.

I see a lot of queued people get pissed off at the drivers who pass them in the empty about-to-be-closed lane and then merge at the end, like they're violating some unwritten rule. I used to be a queue-er, but now I'm a last-minute merger. There's two lanes, may as well use them, right?

Anyway, I'd like to see which strategy works best if everyone would follow it.
posted by ctmf at 7:16 AM on October 26, 2010 [3 favorites]


Wondering why the traffic is so slow?

All the cars are made with Java?
posted by Blazecock Pileon at 7:17 AM on October 26, 2010 [17 favorites]


They merge first, but if nobody lets them in, they fucking squeeze in whether you like it or not.

Change the politeness slider.
posted by eriko at 7:22 AM on October 26, 2010


I'd like to see which strategy works best if everyone would follow it.

Tom Vanderbuilt in his book Traffic argues that last-minute is the way to go. You can read that excerpt on his blog.
posted by Jugwine at 7:28 AM on October 26, 2010 [1 favorite]




I think of the old traffic waves pretty much every. single. day. on my way to work. There's a spot on my drive where it's super slow for about 20 minutes (for a 5 minute stretch). I don't really need an explanation of WHY, what I need is a BUTTON TO PUSH to explode all the other carsnotify the traffic engineers that this spot could use a little work.

The really annoying thing is that a 5 minute difference in when I leave in the morning (which is about 30-40 minutes before I hit that stretch) translates into a 15-20 minute difference in my commute time. And yet I'm apparently physically incapable of leaving those 5 minutes earlier. Even setting my alarm 5 minutes earlier does NOT result in actually leaving 5 minutes earlier. There's always something.
posted by DU at 7:30 AM on October 26, 2010 [2 favorites]


DU, there's a spot I hit once a week when I have to drive up to Kansas City (here's a map of the problem area) that takes around 15 minutes to get through on a good day. The issue there is that first K-10 merges into I-435, then there's immediately an off-ramp to get to I-35, then just past that an on-ramp for I-35 to merge onto I-435.

Oh, and I'm heading for the first exit east of the I-35 merge. So it's the "on-ramp" situation, but repeated multiple times in a very small area.

(though to be fair, it's nowhere near as bad as trying to drive through this... I wasn't all that surprised to find it has its own Wikipedia page as an example of a "problematic interchange")
posted by ubernostrum at 7:53 AM on October 26, 2010 [1 favorite]


Needs more people using the on-ramp/off-ramp/closed lane/turning lane as a passing lane.
posted by specialagentwebb at 7:53 AM on October 26, 2010 [1 favorite]


I disagree with the lane closure scenario. Trucks do not just drive up to the closed lane and stop for long periods of time. They merge first, but if nobody lets them in, they fucking squeeze in whether you like it or not.

Regardless of which, there's no way more than one or two truck drivers would drive past the head of the queue and not let the other truck driver out. There'd only be cars stuck in that inside lane for any length of time once the first truck went past, trucks would be able to get out relatively easily.
posted by Brockles at 7:54 AM on October 26, 2010


I see a lot of queued people get pissed off at the drivers who pass them in the empty about-to-be-closed lane and then merge at the end, like they're violating some unwritten rule. I used to be a queue-er, but now I'm a last-minute merger. There's two lanes, may as well use them, right?

Anyway, I'd like to see which strategy works best if everyone would follow it.


Thats easy. Just watch the entry ramp scenario and wait until one of the cars gets very close (or at) the end of the merge and so has to slow noticeably. Look how much it completely ruins the average speed in the lane the car is merging into. It's much more obvious in that simulation than the lane closing one because it happens on the straight.

The key to maintaining average speed of all the cars is minimising the difference in speed between the fastest and slowest vehicles, so the closer the speed of the closing lane to the free lane, the smaller the disruption will be. As soon as the free lane is slowed, concertina effect (seen clearly in the traffic light one even after the lights go green) means traffic flow is ballsed up. As soon as heavy vehicles are involved, concertina effect is more pronounced (which will happen in closing lanes as trucks are mixed in with cars more). Early merging is better at maintaining average speed than late merging is (particularly for the cars behind you when you merge in late). It amazes me that people can't work this out. Yes, late merging may mean you get through faster, but not for the people behind you and certainly not if someone in front of you is already late merging as the average speed is already screwed. It's a lose-lose for everyone to drop the average speed any more than absolutely necessary.

And yes, I have got all heated about this before.
posted by Brockles at 8:00 AM on October 26, 2010 [8 favorites]


Tom Vanderbuilt in his book Traffic argues that last-minute is the way to go. You can read that excerpt on his blog.

I've read that excerpt and he really doesn't come up with much in the way of justification for that argument beyond it being faster for the late merger. It doesn't address the issue that this screws traffic flow behind the late merger at all, and it baffles me why this is constantly quoted as some kind of truth or worthy reference when it really doesn't have much in the way of proof/demonstrable advantages.

It's only the 'best way' to late merge if you want to get you through the constriction and screw everyone else. It's a catastrophic failure for traffic flow as it slows both lanes of traffic, and 'zipper merging' is only worth it once traffic is already slowed to the stop-start stage. If you want to keep traffic moving, merge early. If you don't give a crap or traffic is already stopped, then you may as well use both lanes as merging has failed by this point anyway.

To immediately go to late merging is either negative thinking or selfish: well, everything will be stopped soon anyway, so fuck all the people behind me, I just want to get to the front of the merge.
posted by Brockles at 8:17 AM on October 26, 2010 [2 favorites]


Me to, Brockles, me too.

If everyone would stagger the cars zipper teeth-like before the merge point, it wouldn't matter if you merged early or late. It's the folks who weld themselves to the car in front of them and refuse to let someone merge in that are the problem, not the later mergers. (IMO)

Given that not everyone is going to follow the optimum strategy, and the people in the polite queue are going to get penalized, it's better for my blood pressure to just drive up as far in the closing lane as I can, position myself between two cars in the queue, and merge at the first opportunity. I think if everyone did that, causing both lanes to fill up, the advantage of one lane over the other would go away, and overall traffic speed would be the same (or even improve, since there would be fewer vindictive not-in-front-of-me! jackasses.)

Very occasionally, though, I entertain myself with a traffic experiment. I maintain that stagger position in the closing lane, matching speed with the other lane, even when mine empties out in front of me. It infuriates drivers behind me, but it seems to make the merge smooth out noticeably to remove the speed differential between the lanes.

That's just when I'm feeling ornery, though.
posted by ctmf at 8:28 AM on October 26, 2010 [3 favorites]


No matter how high I set the politeness slider, I can't get anything approaching real world merging behaviour in any of the scenarios that require it.
posted by jacquilynne at 8:46 AM on October 26, 2010


Given that not everyone is going to follow the optimum strategy, and the people in the polite queue are going to get penalized

The optimum for me, the early merger, is then to straddle the lanes and block people from passing in the soon-to-close lane.
posted by a robot made out of meat at 8:47 AM on October 26, 2010 [3 favorites]


I remember reading about a road in Europe where the engineers made all the speed limit signs digital and modified the speed limit on the fly so that it matched the average speed of traffic, with the supposed effect of annihilating traffic jams. I can't seem to find it now though.
posted by brenton at 8:58 AM on October 26, 2010


I do this obnoxious thing when it comes to lane closures. Assume a two-lane road, and the right lane is closing and we must all merge left. I merge as soon as I can... but only about half-way.

Yes, I take up both lanes. Why? Because if I am merging in, you shouldn't pass me to merge ahead of me. Not only is that cutting in line (yey 4th grade rules) but it also slows the whole thing down for everyone. You save 30 seconds or a minute, but collectively the rest lose a bunch.

I have been honked at, given the finger... and once someone left their car (as we were stopped in traffic) and walked up to my driver's door and berated me. Until the traffic cop came up. The guy told the cop what had happened, and how wrong I was. The cop pointed out that it might actually help, and by the way here's a ticket for leaving your car. =)
posted by andreaazure at 8:59 AM on October 26, 2010 [6 favorites]


It really isn't about merging early or merging late. All that does is change the effective placement of the lane closure and causes the inevitable back-up to be pushed farther back. This assumes that there is enough traffic that slowdown is inevitable even if everyone merges as smooth as possible. So, if traffic is moving steadily, then you should merge late enough that you're not leaving tons of empty road in front of you but early enough that you don't have to slow down much to merge. If, however, traffic is so heavy that things are stop-and-go, I think you need to use all the road.

I think the other key to it is getting back up to speed quickly and smoothly once traffic opens up again.

The lane closure thing is kind of borked in this simulator though. If you have extremely low traffic flows, the car in the closed lane will drive up to the blockage and wait there even though no other cars are coming.
posted by VTX at 9:01 AM on October 26, 2010


The problem with traffic is that drivers can't see or process the other cars outside of a very small radius. Once the computers take over city driving, you'll never have to come to a full stop again--cars will be like electron packets going through a big internet router.
posted by Burhanistan at 9:03 AM on October 26, 2010


I remember reading about a road in Europe where the engineers made all the speed limit signs digital and modified the speed limit on the fly so that it matched the average speed of traffic, with the supposed effect of annihilating traffic jams.

I would imagine that this would annihilate some of the drivers, not the traffic. "Yesterday, the speed limit here was 50 mph, so that's what I'll assume it is today..."
posted by Cool Papa Bell at 9:05 AM on October 26, 2010


I do this obnoxious thing when it comes to lane closures. Assume a two-lane road, and the right lane is closing and we must all merge left. I merge as soon as I can... but only about half-way.

You really, really need to stop doing this. The lane markers are there for a reason. There are two lanes, you need to pick one. You are not waiting in line. This is not fourth grade. You do not have the authority to enforce YOUR idea of ideal traffic behavior on anyone. What you doing is dangerous and irresponsible and probably illegal. If traffic is so slow that someone can walk up your window, then you need to use the whole road. If you want to help, merge smoothly, keep safe gaps ahead of you and keep people from having to slow down to get around your vigilante ass.
posted by VTX at 9:07 AM on October 26, 2010 [7 favorites]


I think the rule should be, everyone must let one car merge in front of them. Those who have not let in their one car should leave a car-length space in front of them to indicate to mergers where to go. Once you've let your guy get in front of you, you can close up the gap. You would also be allowed to drive up the closing lane as long as you could see an available gap to merge into. You're not allowed to pass by a gap if you can't see another one.

Human nature being what it is, it's an unworkable plan of course.
posted by ctmf at 9:16 AM on October 26, 2010


I remember reading about a road in Europe where the engineers made all the speed limit signs digital and modified the speed limit on the fly so that it matched the average speed of traffic, with the supposed effect of annihilating traffic jams.

I think the real problem is that, generally, speed limits don't have much of an effect on actual speeds. I wrote a paper on speeding tickets for a class last year and I remember reading that the correlation between the change in average speed and the change in speed limit is something like .2. I can probably cite that if you REALLY want me to.
posted by VTX at 9:22 AM on October 26, 2010


Traffic waves, physics for bored commuters. Every now and then, when I feel motivated, I'll try his traffic wave experiments but I find the discipline required difficult to maintain.
posted by howling fantods at 9:44 AM on October 26, 2010 [3 favorites]


I don't know what the problem is, if we all drive at 199 km/h and accelerate as fast as possible, traffic flows smooth as silk....
posted by madajb at 10:20 AM on October 26, 2010


I am an early merger just because I like to be a nice driver and not have to force myself into a lane because, well, they're rightfully pissed off at me for not merging early. However, the worst ones are the two late mergers that are glued together that you saw pass you and have not yet been given a chance to merge and suddenly try to merge two at a time in front of you. Now, I usually am nice about letting people in even if they were absolute dicks and took the closed lane, however, in this situation I become the most aggressive driver possible to thwart their evil plans.

I do usually make sure to let in either one or two people in front of me even if they are late mergers though. Just trying to keep the flow of traffic going.

That is all. I hate late mergers.
posted by lizarrd at 10:21 AM on October 26, 2010


DU, there's a spot I hit once a week when I have to drive up to Kansas City (here's a map of the problem area) that takes around 15 minutes to get through on a good day. The issue there is that first K-10 merges into I-435, then there's immediately an off-ramp to get to I-35, then just past that an on-ramp for I-35 to merge onto I-435.

I don't remember that one being such a problem, but granted it's been some years since I drove through it.

I remember the Grandview Triangle being a major pain, but I gather that's mostly taken care of since they reconstructed it.
posted by madajb at 10:22 AM on October 26, 2010


I'll try his traffic wave experiments but I find the discipline required difficult to maintain.

I actually find it very peaceful to try and do the one where you drive at the average speed of traffic rather than stopping and going. I'm not good enough at it to fully master it, but I make it my goal when driving down the DVP in stop and go traffic to never apply my brakes.
posted by jacquilynne at 10:28 AM on October 26, 2010


ctmf wrote: "I see a lot of queued people get pissed off at the drivers who pass them in the empty about-to-be-closed lane and then merge at the end, like they're violating some unwritten rule. I used to be a queue-er, but now I'm a last-minute merger."

In several states, last minute merging in construction zones is against the law. In mine, it's not legal to pass someone less than 1000 or 1500 feet prior to the actual lane closure.

ctmf wrote: "vindictive not-in-front-of-me! jackasses"

You do realize that this jackassery is a direct result of your late-merging jackassery, right?

Generally, I deal with people who refuse to let me change lanes or merge onto a freeway in one of two ways:

When I rent a car, I make sure to get a Crown Vic whenever possible unless I have a specific need or desire for another vehicle. In that case everyone thinks I'm a cop and drives sanely. This even works in Boston. When I'm at home, I usually drive a beat up old car that everyone presumes is uninsured, so they truly believe I absolutely do not give a fuck and will hit them if they don't make the necessary room. (in my state of residence, a driver has a legal duty to make room for traffic entering the freeway and people who are signaling for a lane change, despite the yield signs at the end of the onramp)

Both work very well and very similarly. Activate directional signal, move to edge of lane in signalled direction..suddenly space opens up. M. Azing. This polite lane changing does not work when I'm driving newer cars that people don't mistake for cop cars, sadly.
posted by wierdo at 10:35 AM on October 26, 2010


I should point out that I do generally try to keep an even speed through construction or stop and go traffic so that there is less stop and more go. I am often a fast driver, but never an aggressive driver. I let people draw their own conclusions based on the car I'm driving.

Sometimes this pisses people off who would rather drive 50 for 1000 feet and 20 for another 1000 rather than 40 the whole way, but fuck 'em, they're the ones fucking up traffic flow.
posted by wierdo at 10:40 AM on October 26, 2010


I make it my goal when driving down the DVP in stop and go traffic to never apply my brakes.

I do the same (and also along the stretch of QEW between the Ford plant and Trafalgar), but sometimes find myself reverting to my impatient self. When I do get it right though, as you said, it can be unexpectedly peaceful.
posted by howling fantods at 10:49 AM on October 26, 2010


I remember reading about a road in Europe where the engineers made all the speed limit signs digital and modified the speed limit on the fly so that it matched the average speed of traffic, with the supposed effect of annihilating traffic jams.

Something like this?

posted by greytape at 12:06 PM on October 26, 2010




Tom Vanderbuilt in his book Traffic argues that last-minute is the way to go. You can read that excerpt on his blog.

Bonus: Contains AskMefi shout-out.
posted by Bonzai at 3:16 PM on October 26, 2010


Anyway, I'd like to see which strategy works best if everyone would follow it.

I'm with Tom Vanderbilt. I can't see how moving forward and filling the available space (unless blocking an intersection) can possibly slow traffic down.

I've been a late merger ever since I got my driver's license.

That was a great excerpt. I've seen that book. Now I'll read it! Thanks.

Early merging is better at maintaining average speed than late merging is...

I think you mean "Early merging is better at maintaining a slower average speed than late merging is..."

If everyone would stagger the cars zipper teeth-like before the merge point, it wouldn't matter if you merged early or late.

Amen. It's not a matter of merging at all. It's a matter of filling the available lanes of the road. No one else is using it!

The optimum for me, the early merger, is then to straddle the lanes and block people from passing in the soon-to-close lane.

You are the absolute WORST. You are akin to those assholes who aren't turning right but block the turning lane at stoplights just b/c "oh i dunno, driving makes me an asshole" (fair enough; it does that to most people.)

Now, I usually am nice about letting people in even if they were absolute dicks and took the closed lane

It's not a closed lane! It's a lane that is ending. And it's a perfectly good lane until it ends. (On preview: As wierdo notes, construction zones might be different because there are people working near the closed lanes.)

I'm not good enough at it to fully master it, but I make it my goal when driving down the DVP in stop and go traffic to never apply my brakes.

I used to play this game on the 101 from SF to Mountain View. Not fun, but better than poking yourself in the eye.

Now my daughter's daycare is 2 blocks away, I bike/BART to work, and I don't have to drive at all. More than any other type of people on the planet, I have an unabashed hatred of motorists. Go fuck yourselves.
posted by mrgrimm at 3:22 PM on October 26, 2010


think you mean "Early merging is better at maintaining a slower average speed than late merging is..."

No, it really isn't. You are 100% wrong. If you merge late enough that either you or the driver you are merging with (or those behind him) you are slowing down traffic. If you merge early enough, the disruption to the non-closing lane (in terms of reducing its average speed) is minimal. If you wait until the free lane slows as it approaches the constriction (and so distance between the cars decreases) merging is harder and more likely to need avoiding action/cooperation of the free lane. The biggest single factor that affects the average speed of traffic is the speed in the free lane - especially after it has entered the single lane phase. The higher the post merge speed, the less traffic build up there will be, so late merging and having to slow down or stop at the point of it becoming one lane is what is slowing down traffic - at this point, of course, you are slowing down all the early mergers too, so no-one wins.

If you have to brake to merge, you are slowing traffic. If you can merge without braking (and especially without slowing down first) average speed is maintained. I'm surprised that isn't obvious. The important lane is the post-merge lane, so anything you do to slow traffic in that lane (pre- or post-merge) is bad for traffic flow.

It's not a matter of merging at all. It's a matter of filling the available lanes of the road.

Up to a point, as that's only relevant if the traffic is already stopped, in which case using all the lanes makes some sense, but being as the restriction is the flow of traffic through the constriction (ie one lane) using both lanes really doesn't make much difference at all to how fast traffic goes through the single lane area, just how far back the hold up to merge is. Filling both lanes makes no difference to how fast one line of traffic can move.

Merging is everything to this issue, or it would not be a phenomenon solely related to places where traffic merging. Again, this should be obvious.
posted by Brockles at 4:18 PM on October 26, 2010 [1 favorite]


mrgrimm wrote: "I'm with Tom Vanderbilt. I can't see how moving forward and filling the available space (unless blocking an intersection) can possibly slow traffic down."

The people who you are merging in front of are forced to slow down because you end up making someone slow down to open up space for you. This causes a ripple effect all the way back. This braking is what causes stopped traffic. If nobody ever has to brake for the merge, traffic will merely slow, not stop.

This is why it's becoming increasingly common for construction companies needing to close a highway for a short period for things like stringing wire across to hire police officers to set up a rolling roadblock at an early enough distance and a low enough speed to give them the needed time to work without fully stopping traffic.

When traffic ends up fully stopped, the effects can last literally for hours if the road is congested.

Moreover, you're making it harder for people to do the "right" thing and let enough space open up in front of them so that unexpected stoppage ahead can be handled by maintaining a lower speed rather than constantly speeding up and slowing down. This gets everyone through the area faster. Perhaps I can dig up a simulation that shows this. I know I've seen one before, probably about 5 or 6 years ago. (this is actually the best way, socially, to handle any kind of traffic slowness, not just merges, but it pisses many people off because they don't get it)
posted by wierdo at 4:39 PM on October 26, 2010


I should add that "filling the available lanes" doesn't really help anything at all, unless there's an exit involved somewhere, as there is a finite number of cars that can traverse a given section of road at a given speed in a given time period. Having more cars queued up in the ending lane does nothing to help and often hurts when those in the lane that is not ending have to brake to let people in (or because some jackass cut in front of them driving half the speed of traffic or less because they were nearly stopped in the ending lane and don't have the horsepower and/or gumption to use what they have to accelerate up to speed quickly enough to avoid causing drivers behind to brake)
posted by wierdo at 4:42 PM on October 26, 2010


ctmf: "I think the rule should be, everyone must let one car merge in front of them. Those who have not let in their one car should leave a car-length space in front of them to indicate to mergers where to go. Once you've let your guy get in front of you, you can close up the gap. You would also be allowed to drive up the closing lane as long as you could see an available gap to merge into. You're not allowed to pass by a gap if you can't see another one.

Human nature being what it is, it's an unworkable plan of course.
"

Indeed, that's the problem... Everyone is the single most important driver on the road and must get to their destination as quickly as possible, screw everyone else.

I find it particularly entertaining when a car races in front of me to sit at a red light, and then I (having maintained a slower but still reasonable speed) zip past just after the light turns green, while they're still trying to speed up from stopped.
posted by IndigoRain at 6:01 PM on October 26, 2010


In the one particular merge I'm thinking of, the right lane ends and in the afternoons the left lane backs up quite a way, while the right backs up some, but not as much. At the same time, an on ramp comes on from the right. I like going up the right lane, which once the backup there starts, really only moves about 5 mph more than the left, but consistently more.

Anyway, as I start getting up to the merge from the ramp on the right, I leave at least 2 car spaces in front of me for them to merge in and maintain it the whole way. I find it amusing how many people will come up the ramp from behind me, pass by me with their turn signal on, and pass by the huge gap in front of me, just to get what, by then, is only 2 more cars ahead before the little acceleration lane runs out, and try to wedge in. Then get mad when there's no room. They end up in front of me anyway, all steamed, when they could have just done the easiest thing and taken the space I gave them.
posted by ctmf at 6:55 PM on October 26, 2010


It isn't about merging early or late, that doesn't actually matter. What matters is the people who think they are waiting in line and don't let people merge. The whole thing is about merging smoothly. Think about the delay that letting even 20 cars in front of you would cause, even at 5 mph, it wouldn't materially change your arrival time.

If everyone merges early, you're just pushing the jam upstream farther. You might not see it but it is there. What changes the severity of the jam is how smoothly people merge as it affects how quickly everyone else needs to change speed. If all the merges occur with little braking or accelerating, the whole thing is smoother, safer, and less stressful on everyone.

Stop thinking like you are standing in line, you're not. This is not fourth grade, you are not the traffic police, you are not a traffic engineer (unless you're the Tom Vanderbilt referenced in Jugwine's post). Don't speed up, don't slow down, let people merge when they want, you merge when you can do it safely and smoothly and using most of the available lanes within reason.
posted by VTX at 8:09 PM on October 26, 2010


Methinks some folks need to play with the simulator a bit more. ;)
posted by wierdo at 8:29 PM on October 26, 2010 [1 favorite]


I don't like late mergers, but infinitely worse is a phenomenon I saw often in Chicago, especially on roads like Sheridan: people using the right turn lane to cut in front of everybody. If I was at the front of the line in those situations, I made sure to never let one of those illegal jackasses cut in front. Note that I'm not even talking about merging back into a go-straight lane from the exit/right only lane even though you never intended to exit/turn right. You're still a jackass, but it's technically not illegal (I think). But these people were straight up going straight from a right-turn only lane. Ugh. The worst was one day when I saw somebody doing this but from the left turn lane, which meant he was often in head-to-head situations. I just stayed clear away from that crazy asshole.

And oh, people who use the shoulder to get ahead in traffic jams? Fuck you too.
posted by kmz at 10:18 PM on October 26, 2010


The most interesting experiment is as follows:
1. Set the ramp volume to 150 cars/hour. A traffic jam will not develop at this flow level.
2. Pump up the ramp volume to 1000 cars/hour. Traffic jam appears.
3. Return the ramp volume to 150 cars/hour.

The traffic jam NEVER GOES AWAY.

Interesting how traffic is non-symmetrical in that way, and traffic jams perpetuate themselves long after the cause is gone.
posted by dave99 at 3:57 AM on October 27, 2010 [3 favorites]


The simulator leaves out a key factor - distractedness/situational awareness. Notice how all of the cars maintain more or less the same following distance? That's completely unrealistic.

In the real world, there are huge discrepancies between people who tailgate ruthlessly, and people who lollygag/check their IMs/enjoy a leisurely telephone call at the wheel, and who aren't paying attention to how far the car in front of them is, or the fact that faster traffic is passing them on both sides.

We have a problematic interchange near my house, and I used to get mad at the cheaters (late mergers), but now I think I'm going to join them.

Why? Because there are inevitably several jackasses near the merge point who aren't paying attention to the flow of traffic, and have huge distances in front of them that I can merge into without disrupting traffic. The jackasses who aren't paying attention, and who treat stop-and-go traffic as an opportunity to zone out and take their hands off the wheel deserve to have someone cut in front of them. Might as well be me.

Slightly related, but bears repeating - As a reminder of highway rules, keep right except to pass. If you are being passed by fast-moving traffic on both sides, get to the right - you are driving too slowly, and you need to adhere to lane discipline. If you are unable/unwiling to even drive the speed limit on the highway, stick to surface streets.
posted by etherist at 9:29 AM on October 27, 2010 [1 favorite]


You are akin to those assholes who aren't turning right but block the turning lane at stoplights just b/c "oh i dunno, driving makes me an asshole"

??

Unless it's a right-turn lane, I have as much right to be there if I'm going straight or if I'm turning. That being said, if I see the person behind me wants to turn right (yay to signalling your turns) I'll move over as a courtesy (unless I'm in Quebec, or somewhere where right turns on a red light are illegal.) But maybe I'm not an asshole and just need to turn into the parking lot on the other side of the intersection.
posted by howling fantods at 9:34 AM on October 27, 2010


etherist wrote: "As a reminder of highway rules, keep right except to pass"

Except to pass or to make room for other traffic merging, when it is safe to make said room. As in, check your fucking mirrors for faster traffic about to pass you before changing lanes without signaling. This means you, asshole in Wichita who would have been rear-ended earlier today had I been one of the masses of distracted drivers.

Dipshits really shouldn't drive 15 under. Nor should they trundle up the on ramp at such a speed, as they always seem to do. Yes, I'm saying that idiots should drive faster. Why? Because if we were all moving about the same speed, their idiocy wouldn't be such an immediate problem most of the time.

This is the thread where we complain about other drivers, right?
posted by wierdo at 4:00 PM on October 27, 2010


I don't like late mergers, but infinitely worse is a phenomenon I saw often in Chicago, especially on roads like Sheridan: people using the right turn lane to cut in front of everybody.

Just chiming in as a late mergerer to heartily agree. There's a HUGE difference between taking a lane that's ending all the way to its end and then merging vs. taking a turn lane or exit ramp, etc to the very end and then cutting in.

In the latter case, the drivers are assholes because there's another flow of traffic that's using that turn lane, exit ramp, etc and all the drivers waiting in the proper lane realize that. (Determining the ethical limit of using an exit ramp may be too much beanplating even for me, but I compensate towards politeness and interpret the "exit only" sign itself as the de facto end of the lane.

In the former case (e.g. freeway goes from 5 lanes to 4 as you travel out of the city), it's your social obligation to take the lane to the end and fill the space. As VTX astutely notes, if you don't take the space you're pushing the traffic jam further upstream for no good reason at all.

We have a problematic interchange near my house, and I used to get mad at the cheaters (late mergers), but now I think I'm going to join them.

Why? Because there are inevitably several jackasses near the merge point who aren't paying attention to the flow of traffic, and have huge distances in front of them that I can merge into without disrupting traffic. The jackasses who aren't paying attention, and who treat stop-and-go traffic as an opportunity to zone out and take their hands off the wheel deserve to have someone cut in front of them. Might as well be me.


Amen. It's not just stop-and-go traffic, either. There are people who don't pay attention or don't care. Maybe they drive a lot or like their cars or something. Maybe the problem is that driving is too easy.

The goal of driving somewhere is to get to your destination as safely and quickly as possible and get out of your car ASAP. Just drive the speed limit and pay attention, yo. Make your phone calls before you leave, and eat your lunch after you arrive.

Anyway, for driving, the golden rule(s) applies(y) (whichever version you prefer):

Do unto others as you would have them do unto you
Do not do unto others as you would not have them do unto you
Do unto others as you would have them do unto you, if you were them (I said that first ;D)

Those of us who merge late don't have a problem with other drivers merging late.

I wonder if those drivers who pass on the shoulder or block an exit ramp trying to cut in on another freeway would have a problem if other drivers did it. I would think yes.

It's certainly not perfect, but it's a good smell test for behavior when driving, and smell tests are a good thing. Driving makes people assholes. It makes me an asshole. Just talking about driving makes me an asshole.

Take public transit. Ride your bike. Walk. Stay home. Drive less. It's better for everyone except the car and gas companies.
posted by mrgrimm at 8:57 AM on October 28, 2010


As a reminder of highway rules, keep right except to pass

This means you, EVERYONE IN CALIFORNIA.

"Oh, but I'm in a hurry. The left lane is the fastest. I'm gonna get in the left lane and stay there for the whole trip."

In my travels, I've determined that West Virginians are the best at following this rule. Californians are by far the worst.

Unless it's a right-turn lane, I have as much right to be there if I'm going straight or if I'm turning. That being said, if I see the person behind me wants to turn right (yay to signalling your turns) I'll move over as a courtesy (unless I'm in Quebec, or somewhere where right turns on a red light are illegal.) But maybe I'm not an asshole and just need to turn into the parking lot on the other side of the intersection.

robot made of meat was talking about straddling two lanes to block both intentionally.

What I was referring to is two-lane roads (one each way) where a right turn area (not an official lane) is available at stoplights. Usually, drivers going straight or left will line up at the light, leaving room on the right for right-turners (yes, if they are allowed to turn right on a red light).

I guess some people don't like getting passed, or worry that the people in the right-turn area are going to instead speed ahead and cut everyone off and get to the front or godknowswhat, but some people then position their cars slightly to the right of all the other cars in the line to block the right-turn area. It's basically a "fuck you, I don't care about anyone but me" attitude and possibly paranoid/delusional ("Oh no! That guy's gonna pass me unfairly!")

"Is the motorcar evil? Of course not, because it can have no intentions, no interior life, nurse no resentments, and harbor no malice. In daily life it has become commoner than the cold. In the moral realm the auto lacks pizzazz. It is merely an instrument of evil, crippling or killing thousands every year, consuming many of the resources of the earth; eviscerating cities as routinely as butchers their beef, poisoning the atmosphere, fostering illusions of equality and dominion, encouraging envy and macho competitions, facilitating adolescent fornication, and ravaging the countryside. Its horrid offspring are garages, interchanges, and gas stations. Popular delusions, much destruction, increasing casualties, do not make the motorcar evil, because these consequences were never aimed at. The word in vogue for the damage it does is "collateral." But the most considerable obstacle to calling the car "evil" is that its effects are easily explicable. Carbon monoxide is odorless, but that is the extent of its mystery. The price we pay for our automobiles seems more onerous to us than the cost of their use. Just add air bags and buckle up. Our callous indifference to ruinous truth may be less readily formulated."
posted by mrgrimm at 9:11 AM on October 28, 2010


"Oh, but I'm in a hurry. The left lane is the fastest. I'm gonna get in the left lane and stay there for the whole trip."

In my travels, I've determined that West Virginians are the best at following this rule. Californians are by far the worst.


What I found interesting about driving in Germany is how strict they are at following this rule (presumably because it's strictly enforced?) My wife's German cousin had a minor freak-out whenever I didn't move right fast enough after passing.
posted by howling fantods at 9:22 AM on October 28, 2010


I bet your wife's German cousin was the one sitting in the back seat, so was the one who would get smooshed if someone driving much faster than you smashed into your rear end because you didn't get over fast enough. ;)

To my eternal shame, I do occasionally find myself occupying the left lane when not actively passing. Usually in situations where I'll be passing within 20 seconds or so, but still.
posted by wierdo at 10:18 AM on October 28, 2010


In the former case (e.g. freeway goes from 5 lanes to 4 as you travel out of the city), it's your social obligation to take the lane to the end and fill the space. As VTX astutely notes, if you don't take the space you're pushing the traffic jam further upstream for no good reason at all.

It isn't no good reason at all, because it will raise the average speed of traffic up to and through the constriction by making the merge require less extreme moves on the already merged traffic to allow the merging traffic in.

If you brake, and it causes the person behind you to brake then you will create a lasting drop in speed for the traffic through that point until it is worked out by someone being far enough back to be unaffected by the speed change. If people are close enough, that loss and regaining of speed will have a very lasting affect on traffic speed for some time. This is the concertina effect and is one of the fundamental problems that faces traffic planning. It is known, proven, demonstrated very clearly in the simulation linked to in the OP (and others) and if you deny that late merging has any detrimental affect on traffic speed in the merged lane, you deny the entire concept of concertina effect, which makes you flat out wrong.

Now, merging late with light traffic is perfectly fine. Merging late with medium to heavy traffic is the problem. It is impossibly hard to anticipate matching speed and a gap in traffic and moving into it without causing anyone behind you (before or after the merge) if you are also trying to time that with a hard barrier (such as the lane ending). You have orders of magnitude more chance of merging smoothly if the only variables are your speed and that of the traffic alongside you. It makes sense to remove the time limitation for the merge by doing it early enough that the time taken to complete the move is not being constrained by the chances of hitting the cones. This is early merging. Merging early enough to minimise the speed change to the merged lane is the key to merging early enough to gain the advantages of doing so.

This should be obvious to anyone. I think that at least some of the justification for late merging comes from confusion from the following two scenarios:

1: Traffic is light enough that you can get pretty close to the constriction without altering speed and just do a normal lane change into the merging lane, perhaps even slotting in without even touching your brakes right by the cones.

2: Traffic is so heavy that both lanes are stopped from some of the time anyway

In 1: late or early doesn't make any difference because the merged lane traffic speed is largely unaffected anyway by the merge, but more so from the speed of the slowest vehicle/change in speed limit anyway and there is enough room to bunch the traffic within the constriction to take up this change in speed.

In 2: It won't affect the speed of traffic while you merge anyway, because the difference in speed is also small as it would be in early merging - if traffic has stopped then merging has already failed anyway. But keeping to the late merge will mean that traffic will only speed up after the latest merge point (when everyone has stopped dicking about and just accelerates to the speed limit for the roadwork etc). It's too late to make much difference at this stage.

However, if in the interim between scenario 1 and 2, people make an effort to merge early enough to minimise the impact of their merge into the ongoing lane, point 2 will arise at a later (or higher traffic volume) point than if people merge late. If you don't think this is the case, then unfortunately, you are just wrong.
posted by Brockles at 10:50 AM on October 28, 2010 [1 favorite]


Vanderbilt is not a traffic engineer. He prefers late merging but offers no argument for it in his book. Brockles has provided much more analysis here.

Vanderbilt, and others, think that not taking a closing lane to its end is wasting road capacity. This is wrong in an argument about throughput capacity. A lane that is closing has no throughput capacity. (It does have storage capacity.)

Merging from an on ramp to a highway is similar, in some cases, to a late merge. Or, at least, the difference between a late merge and an early merge is small for this case. There is a very limited section of pavement available for the merge, the gap for merging has to be available at just the right time and it can be difficult to get the speeds of vehicles matched. Do these merges go well ? No. For medium or heavy traffic, the merge always slows everybody down.
posted by llc at 12:13 PM on October 28, 2010


A lane that is closing has no throughput capacity. (It does have storage capacity.)

Then why drive on it 1 mile before it closes? Or 10 miles before it closes?

What's the difference in driving on it until 500 feet before it closes?

Or, a more proper response might be: "When does a closing lane lose its throughput capacity?" How many miles/feet/meters before it ends?
posted by mrgrimm at 12:23 PM on October 28, 2010


It isn't no good reason at all, because it will raise the average speed of traffic up to and through the constriction by making the merge require less extreme moves on the already merged traffic to allow the merging traffic in.

I guess this is where I disagree and don't see how you've proven that.

Why does it matter *where* people do the 1 car from this lane/1 car from that lane zipper? Traffic is always going to slow down at the merging point? Why shouldn't it be as late as possible?

Also, merging later allows drivers in the lane that getting merged into move other further to their left (if possible). That is, you have 5 lanes of traffic narrowing down to 4, I think the ideal situation would have 20% of traffic in each lane to start, then 25% in each lane when the lanes reduce.

So, when that 20% of the total traffic moves from lane 5 to lane 4, a big chunk (37.5% (or 15% of the total traffic)) of that lane 4 combined traffic will need to move over into the other lanes.

Merging later seems to give the lane 4 drivers more time to move into lanes 1, 2, and 3.
posted by mrgrimm at 12:29 PM on October 28, 2010


Why does it matter *where* people do the 1 car from this lane/1 car from that lane zipper? Traffic is always going to slow down at the merging point?

Because the less room you have available for the merge, the less able you are to plan to do so in a away that doesn't disrupt the flow of traffic - it's not just about getting into the lane, it's about doing so without making the person you get in front of have to slow to accommodate you more than necessary.

The importance is to move over before the speed differential between your lane and the one you are joining gets great enough that they have to alter their speed more than the restriction itself demands. So if your speed drops below, say, the 50mph of the road works/construction then you left it too late to merge and have slowed traffic down. There should be no reason, with enough space between vehicles and considerate merging at comparable speeds, that traffic wouldn't just slow to 50mph and carry on through the road works. But you get a much slower speed at the entrance to the construction and people accelerating back up to 50mph inside the zone because they had to slow down to let someone in from the closing lane. Traffic is slower overall.

If you can't get this, then imagine which of the two is easier:

1: merging onto a highway with a 1 mile long entry lane/slip road/on-ramp that allows you to get up to highway speeds before you have to merge.

2: Merging onto a highway from a side road that has a sharp turn at the merging point and is only 150yards long (limiting your ability to accelerate to the same speed as the other cars).

Do both have the same safety aspects to you? Do you think that it is as easy in example 2 as it is in 1? Of course not. Because the speed differential in 2 make it pretty hairy to get into traffic without worrying about a truck slamming into the back of your car, or (if you are already on the highway and approaching this merge) you would most likely have to slow down to accommodate the merging traffic. If the highway only has one lane, then ALL traffic is slowed by the car coming onto the highway. This is the same as a lane closure. Where possible, you'd choose the on-ramp in example 1, yet don't when it comes up to a lane closure.

Merging later seems to give the lane 4 drivers more time to move into lanes 1, 2, and 3.

No, merging earlier will trigger people to move across as people come into their lane. Otherwise people are simultaneously trying to move into the lane from one side, or out from the other. Often you see this as the lane nearest the merge is almost stationary and people are nipping into fast moving traffic from it to try and keep going. This is a result of people late-merging into that lane from the other side, not from early merging. Planning ahead is always, ALWAYS, more efficient. After all, why on earth would people move out of lane 4? Would they do so to leave a completely empty lane for everyone in lane 5 to merge into at the last minute en masse? Of course not.

To merge early triggers the redistribution of traffic into the other lanes earlier, and so gives more time for it to happen and means that it happens sooner. Often, when merging in this manner (and with a fast enough car) you can get over two lanes straight away and floor it to keep up with traffic and watch the rest of the snarl up at the front of the queue on the inside two lanes as too much traffic is trying to get into the space at the end of the merge lane. Try it for a while, and notice how much quicker you get past that snarl up if you get over fast, and get over two or more lanes when a closure is happening. It may surprise you.

posted by Brockles at 1:05 PM on October 28, 2010


My HTML appears to have left the building. Hopefully it's penetrable without it...
posted by Brockles at 1:15 PM on October 28, 2010


mrgrimm, It doesn't matter how long a road is that doesn't go through, it still doesn't go through.
The throughput capacity of a one lane road is one lane's worth. The throughput capacity of an eighty lane road, that is reduced to one lane, is one lane's worth.
posted by llc at 4:15 PM on October 28, 2010


While the overall throughput is optimized by early merging that doesn't factor in human behavior. Some people will merge late to gain the best individual advantage. So your options are to either A) be altruistic and do your part to make the traffic flow as quickly as possible for everyone or B) merge at the last second and get home early.

Since there are always going to be some B drivers the open lane will not be flowing at maximum capacity no matter which of these options you choose. You can not force everyone to be an A driver.

Therefore, the best strategy for an individual is to be a B driver. The more A drivers there are the better it will be for you.
posted by Bonzai at 9:34 AM on October 29, 2010


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