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Merging Traffic Lanes
April 25, 2005 12:40 PM   Subscribe

So I've been noticing for some time that whenver I'm on the highway and encounter some kind of construction or whatever that forces one to merge, that if I dutifully merge over as quickly as possible I then watch as people in the lane that is bound to run out move past me. I'm wondering why this is so -- why people are rewarded for merging at the last possible moment. As it seems that usually at the merge point the two lanes take turns as far as which car moves forward, it seems that the two lanes should move at the same speed. Can anyone explain why this doesn't seem to be so?
posted by jgballard to Travel & Transportation (60 answers total) 11 users marked this as a favorite
 
I've noticed this phenomenon before, and there must be some human psychology going on here. Maybe everyone in the "long lane" were hardcore commuters and got burned once before trying to go into the open lane. I.E. they'd rather take the sure thing rather than risk getting shut out.

On some level it must be related to rubbernecking. Somewhere in this list of interviews might be an answer.
posted by jeremias at 12:50 PM on April 25, 2005


You've just called on one of my pet peeves.

The more I'm on the road (my job sends me out for about 600 miles a week) the more I believe this is just two forms of human nature in effect. You've got one set of people who have realized that if they blaze up to the end, someone will let them in and they'll be further ahead than if they had merged back where they should've.

The other set are the people that let them in. "Oh, look at this poor guy here. He didn't notice the mile's worth of 'MERGE-THIS LAND ENDS SOON' signs and now all these meanies aren't letting him in.

Of course, the first set could be those frustrated like us, who've just decided to say "screw it - I might as well wait 'til the last minute like everyone else."

As for me, I merge as soon as possible, then pick a second merge point. If you're still in the merging lane by the time we get to that point, I will drive you into the big orange trucks before I let you get in front of me.

Then again, I've grown to generally hate and mistrust everyone else on the road.

On preview: jeremias, generally it's the other way around - people will stay in the lane that's ending because it's the faster moving lane. They don't want to wait with everyone else, so they zip down the faster lane. I see it all the time going home from work, where my exit is an "exit only" lane.
posted by Moondoggie at 12:57 PM on April 25, 2005 [2 favorites]


I figure the ideal situation would be that both lanes keep going until the lane that has to merge runs out--that way, the maximum amount of available road is used. Then, merging should proceed in an orderly "zipper" fashion, alternating equally between the lanes. It's not complicated, really.

Unfortunately (and this is the answer to your question), people suck. They'll try whatever they can to pass you, to better enjoy the traffic jam from a few car lengths ahead of you. The commonly argreed-upon merge point will usually happen a ways before the lane runs out, and the majority of people will go along and merge. People who feel that they have more pressing concerns and are generally more important than you will keep going, and some weak-spined schmuck will let them in further down, slowing your progress even more. This sucks; I'm afraid it's the way of the world.
posted by muckster at 1:01 PM on April 25, 2005


Because of people like you who merge early, basically.

Assume the lines each have one hundred cars in them. If you shuffle merge at the last point, everything is even.

But you, being the eager beaver that you are, moved over somewhere a mile before that point. Now line 1 has 101 cars in it, and line 2 has only 99. Because you've been in the line for awhile, when you get to the front, you have to let someone from line 2 shuffle merge in front of you, meaning that two cars got over from 1 to 2 in the space where only one should have. Plus, though, the guy who let you in now has to let another person in. That's three! Three cars where only one would otherwise have merged.

It doesn't take a lot of early movers before lane 2 is emptying out faster than water bucket at the OK corral.
posted by jacquilynne at 1:01 PM on April 25, 2005 [2 favorites]


Because normal, unselfish people see a sign indicating that the left lane will end and get in the right lane at their earliest convenience.

Selfish people know that decent people will do this and use the situation to their advantage. If the guy behind you falls in line when you do, he'll get through the obstruction at about the same time you do.

However, if his sense of entitlement allows him to bare down and drive right up to the barrier obstructing the closed lane, most people will have already merged and he'll have a clear path to the obstruction. At that point, he only needs to find one person stupid or slow enough to let him in and he's through a lot quicker than the considerate people. And generally at the expense of the considerate people because he's the reason that they stop completely (rather than slow down).

Not that you asked, but these people should be dragged from their cars, be punched repeatedly, have their skull broken on the pavement, be urinated on and then left for the ants. Make no mistake, they are leeches and should be treated as such.
posted by Mayor Curley at 1:05 PM on April 25, 2005 [4 favorites]


I think you answered your own question. Everyone knows they won't get stuck for days on end if they wait to merge until the last minute. Instead, someone will be nice and let them in. We all know this, but most of us feel like waiting until the last minute is somewhat rude, so we merge early when it's most convenient for everyone involved, not just ourselves.

So, the people you watch pass you are counting on the niceness of other people (like ourselves) to let them in to the lane in the future.

On further reflection, the fact that the lane that ends soon is always moving faster than the other lane is proof that there are more considerate people driving around than there are inconsiderate (those who don't merge until the end). The congestion and slowness is a result of all these people being nice at once, and merging dutifully. Hmm.

On preview: I also let people in no matter where they decide to merge. Yes, I disagree with their handling of the situation, but I'm also just a nice guy.
posted by odinsdream at 1:05 PM on April 25, 2005


Isn't it obvious that the best thing to do is for both lanes to be full right up to the last moment, and then merge in turn? That way, the full capacity of the road is being used, and it's fair on everyone, rather than a bunch of people merging early and trying to create an artificial one-lane road earlier than necessary.
posted by chrismear at 1:15 PM on April 25, 2005 [3 favorites]


We all agree that a one-and-one merge at the actual point of constriction is fair, right? That it's the safest, most predictable, well-ordered way to merge two lanes of easily-confused human drivers?

Then if you merge before that, you're a fool; if you then complain that you're being taken advantage of, you're a damn fool and a whiner. And if you block someone from merging when they are clearly ahead of you, signalling, and you could just as easily let them in, you're an asshole and a hazard on the road.

Stay in your damn lane till the merge, then alternate cars politely.
posted by nicwolff at 1:17 PM on April 25, 2005 [1 favorite]


I stay to the right for as long as possible, but match speeds with traffic in the left lane, preventing the dickheads from speeding up. Usually somebody in the left creates a gap I ride with, right up to the merge point. Sometimes, I'm passed on the right, on the shoulder, by one of the frustrated.
posted by Rash at 1:18 PM on April 25, 2005 [1 favorite]


these people should be dragged from their cars, be punched repeatedly, have their skull broken on the pavement, be urinated on and then left for the ants.

Every ant, from Rockport to Rochester, would feast long and full on the carcasses of Massholes.
posted by trharlan at 1:23 PM on April 25, 2005


Somewhat interesting discussion of the legal aspects (at least in Michigan) of the last-second merge recently in the Detroit Free Press.

I hate last-second lane mergers with the passion of 1,000 suns. The implicit message is that those of us who got over early have nothing better to do, while the late mergers have more pressing business. I'm like Moondoggie -- I will let people in a reasonable distance before the final point (particularly where it looks like their failure to get over was inadvertent), then will ride the bumper of the car in front of me until the merge (which usually only results in the car in front of me letting the person in, thus giving me two people to seethe at).
posted by pardonyou? at 1:30 PM on April 25, 2005


It's not really a good vs. bad opposition, it's a stress versus no-stress choice. I usually merge at the last minute because I can usually deal with the tension of looking for the gap and moving in on it. When I'm tired, on talking on the phone (on my street-legal hands free), or just pleasantly absorbed in something on the radio, I merge early, and don't have to sweat it.
posted by MattD at 1:31 PM on April 25, 2005


jacquilynne has it right (and I see her answer has been marked as best). Otherwise, the best thing to do would be to merge 10, or 100, miles in advance. It's to everyone's advantage to use the road fully.

I do not understand the logic of ones like Rash--what, since you're too timid to wait until the last minute, no one else can do what the traffic engineers have decided is best for the flow of traffic?

A different situation occurs when there is an exit-only lane with slow-moving traffic. There, one should get in line and wait one's turn. But there's really no justification to merge early other than a mistaken notion of fair play.
posted by MrMoonPie at 1:41 PM on April 25, 2005 [1 favorite]


Since we do agree on the premise, I can see nicwolff's point. I suppose the question becomes, do you adapt to the way things ought to be (everybody should merge at the last minute), or to the way they really are (the majority merges early, usually a little ways after the first signs are posted.) The problem with the idealism defense of late merging is that it's also terribly selfish. The problem with accepting the herd's choice of an early merge point is that it's less than ideal, and you're likely to get screwed.
posted by muckster at 1:48 PM on April 25, 2005


Well put, muckster. In actual practice, I do choose a point somewhere in between immediate and last-minute merging, and it does depend more-or-less on MattD's formula. Then, of course, I get pissed at the assholes who choose a later point than I did, and I do everything in my power to keep them out. I am, at least, aware of my hypocrisy.
posted by MrMoonPie at 1:54 PM on April 25, 2005


We all agree that a one-and-one merge at the actual point of constriction is fair, right?

I sure as hell don't. Such a thing only results because some people are being assholes, who I too detest with supernova fury.

That it's the safest, most predictable, well-ordered way to merge two lanes of easily-confused human drivers?

Purest horseshit. The safest, most predictable, well-ordered way for two lanes to merge is for them to merge in short order upon seeing a decently-spaced warning sign, when both lanes have plenty of room between cars, and to maintain a safe following distance. Not to rush to the end setting up a "one and one" merge that, of course, only happens when the cars are stopped.

And if you block someone from merging when they are clearly ahead of you, signalling, and you could just as easily let them in, you're an asshole and a hazard on the road.

The idea that calmly insisting on retaining your right-of-way while moving straight ahead without changing lanes or otherwise turning is being a "hazard" is likewise purest horseshit.

I have the right of way at that point, and you, Mr. Rushy-Aheady Driver, don't. Suck it. You could have merged in at any point in the past, but you didn't, because you're a fool and an asshole.

I love it when truckers set up Asshole Blocks in long merges. I loved it even more when once in Durham I saw a car pull into the disappearing lane and get trapped there as the decent people accelerated up to around 40 and left him there eating exhaust.
posted by ROU_Xenophobe at 1:57 PM on April 25, 2005 [1 favorite]


As to what is most efficient: the scenario described is not.

I commute a long distance in Denver. A couple of years ago, a multi-year, huge construction project, T-Rex, started. They tore up the road something awful.

Amazingly, traffic improved. Why?

There used to be several long, exit-only lanes. Selfish a**holes would merge right into those lanes, zoom along, and cut back into traffic at the last possible moment, often across a solid line. Every time they do this, somebody has to hit their brakes to let them in, and it creates a traffic wave that propagates backwards.

When T-Rex closed down all these lanes - made LESS space available for cars, traffic actually IMPROVED because those a**holes had to just stay in their lane instead of pulling this stunt. Nobody had to slam on their brakes, so fewer traffic jam wave artifacts.

Anway, it's a classic prisoner's dillemma. The idea that "fair play" is a mistaken notion is false. If these few people weren't acting so selfishly, everyone (including them!) would really be better off.

The only solution is tit-for-tat. Everytime you see one of these folks and you have it in you, punish them. Don't let them in. Don't let the obsessive lane changers do it. Make their lives hell every time. Change the incentives.
posted by bradhill at 1:59 PM on April 25, 2005


Always trust the truckers -- very rarely are they late mergers.

So what about the people who are in the big line, but leave half of the car out in the other lane so that other people can't go by? Essentially, this creates a merge point ahead of the actual one where the lane shuts down.

Part of the problem? Part of the solution? I've seen truckers do it before and they generally know what they're doing. But some of the discussion here leads me to think it's not a wise policy. It certainly feels just. What do you all think?
posted by ontic at 1:59 PM on April 25, 2005


A number of recent studies show that late merging is more efficient during congested traffic, giving increased throughput in the region of 20%. However, early merging is still good when the traffic is free-flowing.

"The so-called 'late merge' concept has been thoroughly studied and tested by traffic engineers, and there seems to be widespread agreement that it works well, particularly when high-volume traffic needs to be funneled from two lanes to one."
from Merging later rather than sooner is better, a newspaper article.

"'So far this system has proven to help traffic flow by decreasing queue lengths as much as 35 percent. It has also reduced lane-changing conflicts and sudden-stop crashes,' said Craig Mittelstadt, Office of Construction and Innovative Contracting. 'However, it can only work properly if drivers comply with the messages.'"
from Drivers can help reduce delay time in work zones by following “zipper” approach, a news release by the Minnesota Department of Transport.

Get with the programme, people!
posted by chrismear at 2:29 PM on April 25, 2005 [1 favorite]


What do you say to that, ROU_Xenophobe? Are the cited traffic engineers full of nicwolff's (and, by extension, jacquilynne's and my) "purest horseshit"?

You didn't specifically refute anything anyone else said. Your post translates more-or-less as "it feels wrong, and I don't do it, so it is wrong, and no one else should do it."
posted by MrMoonPie at 2:36 PM on April 25, 2005


The people who wait until the last minute to merge scare me. Merging in that situation is very stressful, and to wait until the last minute requires that one be blissfully unaware of the burning hatred of a hundred glares, i.e., a sociopath. And who knows what a sociopathic driver will do?
posted by kindall at 2:38 PM on April 25, 2005


Always trust the truckers
Truckers are generally driving trucks, which are wide, long vehicles with poor rear visibility. It is difficult to change lanes in a truck in heavy traffic -- you have to wait for a large gap. The most appropriate driving styles for trucks and cars are often very different.

posted by chrismear at 2:41 PM on April 25, 2005


Isn't it obvious that the best thing to do is for both lanes to be full right up to the last moment, and then merge in turn? That way, the full capacity of the road is being used, and it's fair on everyone, rather than a bunch of people merging early and trying to create an artificial one-lane road earlier than necessary.

I was fascinated to see the 'zipper' phenomenon in action on the Autobahn, in a construction zone.

Instead of the usual asshole American behavior - I'll just run up the open lane as far as possible and someone will let me in or the flip side, I'll run you into the barricades - I saw people taking turns. One car from each lane. Like a fucking ballet. Instead of slowing from 65 to 5 to accomplish this, we slowed to maybe 20.
posted by fixedgear at 2:43 PM on April 25, 2005 [1 favorite]


Always trust the truckers -- very rarely are they late mergers.

Yes--but also note that truckers almost always calmly let the late mergers in ahead of them, rather than trying to block them out. Ever notice the big gaps in front of semis in the slow lanes where the truckers are letting in the late mergers? (Often larger gaps than would be needed for a large semi to stop, or which could be explained by a truck's lower acceleration, so you can't explain it solely on account of those.) Leaving plenty of room for the late mergers allows them to merge at a reasonable speed, which is ultimately less disruptive than trying to "punish" them, which causes them to merge at a very low speed, causing people behind them to have to also come to a (near-)stop.

So yes, do trust the truckers--and don't try to punish the late mergers.
posted by DevilsAdvocate at 2:52 PM on April 25, 2005


I watched this phenomenon play out in Austin when a busy 2-lane road which I regularly commuted was reduced to one during a year of construction.

Interestingly, after a few weeks traffic engineers placed signs along the road telling drivers to use both lanes up until the merge.

+1 for the late mergers.

It's my belief that the behavior the causes the longest backups are people in the moving lane being vindictive towards others who choose to merge after they did, and block them out causing an unneccessary jam in the merging lane.

The best situation always is the perfect zipper. Exiting parking lots, merging, entering the freeway. Life would be good if people used the zipper.
posted by FearTormento at 2:53 PM on April 25, 2005 [1 favorite]


This is the thing: the 'invisible hand' works in driving situations, but only up to a point. As RUO_Xenophobe points out, although with more road-rage than is worthwhile I suppose, simply being a selfish driver will not make the road a better place. I live in Boston, where people follow the "look out for number one" rule to the letter. This results in more run red lights, dead pedestrians, et cetera. They would be infuriated in the backroads of Colorado, where I grew up; people there just drive too slow, at least according to Boston wisdom.

Everybody wants to get where they're going. So it appears to me that the best thing to do is this:

I wait until a safe point to merge. It takes some care; I have to think about the speed I'm going, and the speed everyone else is going. I have to think about everyone else's safety and convenience as well as my own. I don't want to wait until the last minute, because that's exceedingly dangerous; I don't want to go too early, because that's won't get me where I'm going any faster. Then, at the exact moment that I've determined is the safe place to merge in this situation, I merge. Halfway. The people behind me in either lane can't swerve around me that way. If they're aching to, I know it's unsafe, and they shouldn't be doing it anyway; they'll only kill someone. So I let them yell at me; it's only a few moments before we're past the merge anyhow.

That's how I do it. YMMV.

On preview: FearTormento, that's interesting. I've almost always seen the opposite problem; it's far more dangerous to merge late than merge early, and I can't count the number of potentially fatal accidents I've seen almost result from late-mergers.
posted by koeselitz at 2:56 PM on April 25, 2005


I'm a medium merger: I don't merge right away, but I don't wait until the last minute. After I merge, I'm a selective merge-allower: if you're a late merger driving an SUV, prepare to merge in front of someone else, because I'm not letting you in. Most other people, especially if they signal in advance and maybe glance over in my direction with a pleading look on their face, I'll let in. Mean-spirited and capricious? Perhaps, perhaps, perhaps.
posted by goatdog at 2:57 PM on April 25, 2005


Also, a 'perfect zipper' is a lot like a perfect state; a nice idea, but extremely rare, and almost impossible to fabricate. I've never seen it, and I've driven from California to Maine.
posted by koeselitz at 2:57 PM on April 25, 2005


Also note the Traffic Waves site (with a specific page on Merge Jams).
posted by DevilsAdvocate at 2:58 PM on April 25, 2005


Anything that causes other users to brake will cause slowdowns on a freeway. The big problem is not leaving enough space between vehicles so that if a car ahead slows down then you have to brake. Repeat behind you & so on. Concertina effect.
posted by i_cola at 3:11 PM on April 25, 2005


I'm a nice guy, really I am. If it looks like you just made a mistake and now need to merge later that's no problem at all, however if you are the only person in some gross-out disgusting SUV I don't even see you.

While I do realize that using both lanes up to the merge point is the best use of space it seems to slow down the flow, ie: if everyone is merging when they can traffic can maintain a higher rate of speed than if both lanes are full to the merge point and are then zippering, has no one else noticed this?
posted by Cosine at 3:53 PM on April 25, 2005


I just got my first license last month, so this is all new to me, but I tend to merge conservatively (early) because it seems less stressful, and as an inexperienced driver I like to minimize the number of distractions. I was also taught to leave a large space between me and the car in front of me for safety, so I get merged in front of a lot. Since I drive the 520 every day, I have learned to recognize selfish assholes, and I tend to close up that gap (when it feels safe to do so) just enough to annoy them. I generally tend to be generous and nice, but only to people who deserve it.
posted by matildaben at 4:05 PM on April 25, 2005


What do you say to that, ROU_Xenophobe? Are the cited traffic engineers full of nicwolff's (and, by extension, jacquilynne's and my) "purest horseshit"?

(1) The articles both note that it's for use in congested areas, ie where you're already stop-and-go or close to it. At that point, sure.

But it still pisses me off to no end when I'm driving along a rural interstate in light traffic and end up in a long delay because someone ran to the end, forced someone else to brake, and set up a chain of brakings that resulted in a mile-plus line of stopped cars, when if those fuckers at the end had just merged ahead of time there wouldn't even have been a slowdown. As I drive round-trip between D/FW and Toronto several times a year through darkest Oklahoma and Missouri, this is something I see frequently.

(2) The McCall's article points out that the problem with a get-over-early system is, itself, the goddam late-mergers rushing to the end and stopping things up. If they hadn't been being pricks to start with, it would have worked fine, at least outside congested urban freeways.

As an alternative to an unmanaged stop-and-go situation, sure, it makes sense to take turns. But, most of the time, we wouldn't even be in a stop-and-go if it hadn't been for jerks rushing ahead.
posted by ROU_Xenophobe at 4:06 PM on April 25, 2005


I have seen signs at certain construction sites that tell drivers not to merge until the last minute, and then to take turns. People were surprisingly good at taking turns then. I've always figured that the traffic engineers in charge of that construction site knew exactly what they were doing.
posted by grouse at 4:12 PM on April 25, 2005


In the Okanagan Valley, BC, there is a choke-point on the very busy highway: a 1km bridge that is three lanes (one lane reversing) wide. It is brutal.

The highway department, via television and radio and signage, encourage drivers to fill both lanes and merge at the latest time to facilitate traffic flow.

As always, there are ROU-style wingnuts that shit themselves blue when the locals drive the way the traffic engineers have told us to drive.
posted by five fresh fish at 4:50 PM on April 25, 2005


As always, there are people who can't see the difference between driving in already congested conditions, and driving in congestion that would not have existed but for bad driving.
posted by ROU_Xenophobe at 5:05 PM on April 25, 2005


I stay to the right for as long as possible, but match speeds with traffic in the left lane (the right lane being the one that's closed)

Yeah, I do that too sometimes, on those rare occasions when I drive on that kind of road. When it works, it forces traffic into that "perfect zipper" state, at least for a little while.
posted by sfenders at 5:25 PM on April 25, 2005


I meant what I said up there about one-and-one merging to apply to dense, slow-moving traffic - which is clearly what jgballard was referring to in the question with "at the merge point the two lanes take turns as far as which car moves forward". Anyway, I drive mostly around New York City and on Interstate 95 and the New Jersey Turnpike, so the last time I saw anything else was a while back.

But off in ROU-land, we're all driving along at 55 to 65 per when we see a "LANE ENDS - MERGE RIGHT" sign. He and we and all the other right-thinking drivers merge right, except for one asshole who stays in the passing lane and zips past all us good Christians only to cut into our lane at the last moment. Since we are still moving at 55 per, but at twice the density we were comfortable with before we merged, this causes the driver of the car he cut off to hit the brakes, which causes traffic approaching the constriction to slow as those drivers see red.

And soon we've got stop-and-go traffic since the merge has moved right up to the construction site. Now if we don't want that to happen, we can do one of a few things:

1. We can hope that traffic engineers replace the "LANE ENDS - MERGE RIGHT" signs with "DO NOT PASS - MERGE RIGHT" signs in an effort to force the "ideal" high-speed zipper merge. They don't, though, and I assume it's not because no-one's thought of it.

2. We can let the drivers who are still in the passing lane when it ends merge gracefully at speed, instead of making them squeeze in. This would mean accepting that there will be late-mergers, and not following too close.

3. We can TEACH THOSE PRICKS A LESSON! by DRIVING REAL CLOSE TO THE GUY IN FRONT so they can't merge at speed but instead have to stop short and then merge from zero. Of course, this will totally fuck up this merge and guarantee the result we were trying to prevent, but maybe in the future these JERKS WILL MERGE EARLIER. Also, forcing another driver to stop MAKES YOUR PENIS BIGGER.
posted by nicwolff at 5:54 PM on April 25, 2005


But off in ROU-land, we're all driving along at 55 to 65 per when we see a "LANE ENDS - MERGE RIGHT" sign.

You say that like it's obviously weird beyond belief, but I've had this happen well in excess of 20 times on rural interstates. It's a regular fixture of DFW-Florida, DFW-Toronto, and DFW-RDU express runs out in the middle of nowhere.

It's immensely frustrating to be moving along at 70 with a car every, oh, maybe quarter or eighth of a mile and see the merge sign at a point where if people would just merge over, there's actually enough room in the single lane for traffic to continue at speed -- nobody has to slow down any appreciable amount at all, except for the people trying to do 85 or 90 in a 65. And yet, even though nobody has to actually be slowed down at all, we all get to spend an hour going a mile because some yutz three hours ago decided that this shit didn't apply to him.

Actually, I've seen signs on 70 through IL or 44 through MO
(or both) where they say "RIGHT LAND ENDS 12 MILES" and then "RIGHT LANE ENDS 8 MILES ***MERGE NOW***", and lo and behold it actually seemed to work, somewhat. The crunchup was smaller anyhow. ISTR similar signage on the turnpikes in OK, where merging is rarely a problem.
posted by ROU_Xenophobe at 6:26 PM on April 25, 2005


Also a regular occurrence on RDU-FLA and RDU-DC runs, back when I did those. Especially annoying on 85 between Durham and Petersburg, which has very light traffic through absolutely fuck-all.
posted by ROU_Xenophobe at 6:29 PM on April 25, 2005


While the "zipper" approach may make the most sense, this isn't a perfect world. People will not comply because they don't give a fuck in this "Me Me Me!" world. They deserve to be punished as Mayor Curley explained. However, he left out a step in the punishment phase - a traffic cone should be set on fire and shoved up his or her ass after being pissed upon (we wouldn't want to put the fire out).
posted by deborah at 7:51 PM on April 25, 2005


I make my own zipper situation, by leaving a merge-sized space between me and the car ahead. That's whether I am in the disappearing lane or the continuing lane. Then I just follow the car ahead at that distance. When merging happens, either I let one car in ahead of me and continue at whatever speed traffic is moving, or (almost invariably) a person in the merge-to lane sees what I'm doing, and lets me in.

Getting all heated because someone else gains an advantage of a few seconds is just as pointless as expending a lot of energy gaining that advantage.
posted by Kirth Gerson at 7:57 PM on April 25, 2005


Doesn't compute, ROU - if the cars were that sparse "three hours ago", then that first speedy yutz who merged late didn't have to cut anyone off. And even if he did, if cars are 10-15 seconds apart there's no way that would make the cars behind slow down and cause the jam.

And getting cut off only make you slow down for a second; once the yutz zooms off down the lane you speed right back up. So if you don't get the brake-light cascade, there's no jam.

No, I propose that the problem in those situations is in fact timid drivers who, when the highways gets down to one lane, slow unnecessarily. It takes exactly one driver slowing from 70 to 60 as the cones close in on them to cause a pile-up at the merge, and once that one-and-one merge pattern is triggered, it's semi-permanent.

How did a Rapid Offensive Unit become such a meek tactician in 2-space?
posted by nicwolff at 8:02 PM on April 25, 2005


Sort of off the topic, but back in the day I worked at this orchid nursery way outside of the city I live in, a good hour+ commute. I carpooled with two other urbanites. On the way back into town there was a "exit only" lane that tended to get abused in just this fashion, cheaters zipping into it to jump the line (traffic got balled up in a later, stoplight-regulated exit shortly thereafter). I and one of my fellows were staunch opponents of this tactic - exit only means exit only! Staying in the lane with no intention of exiting is cheating! The other coworker invariably took the lane while we righteously berated her on her accumulating debt of bad karma.

One day two of us drove (can't remember why, I think one had to come in late that day) and left at the same time. We hit the exit lane at about the same time and of course, she took it and we (I was a passenger) stayed in our actual exit lane. And you know: when she had rushed ahead and jammed herself back into traffic, and we finally got to the light, she was about five cars ahead of us. It made me realize that most of the crazy jerky stuff people do on the road has no significant impact on their trip time. It is purely about this need to feel that you are getting ahead.
posted by nanojath at 8:49 PM on April 25, 2005 [4 favorites]


nanojath, as the traffic breaks up, your exit-lane-using friend gets lets say one extra minute to drive aggressively, so lets say she gets home two minutes earlier than you. Times say 200 work days = 6h40m of time saved each year. How much accumulated bad karma is that worth?
posted by nicwolff at 9:21 PM on April 25, 2005


One problem with traffic is that it does not follow Bernoulli's Principle. When the apeture shrinks, it should move faster.
posted by Eideteker at 9:32 PM on April 25, 2005


And even if he did, if cars are 10-15 seconds apart there's no way that would make the cars behind slow down and cause the jam.

They were. Now they're at urban-freeway distances; ie a little too close and looking ahead of the car in front of them. So, yeah, you get the brake-light cascade.

No doubt timid drivers and a lower limit in the zone play a role too. But everyone could still have gotten through with no stopping, dammit!

How did a Rapid Offensive Unit become such a meek tactician in 2-space?

There are stupid rules against me just effectorizing your brain until you agree with me and find me fabulously attractive. Would you believe I'm not even allowed to CAM-dust people who disagree? The nerve!
posted by ROU_Xenophobe at 10:02 PM on April 25, 2005


Waitaminnit - if there's a lower limit in the construction zone, then you're asking drivers to declerate and merge without ever jamming (remember, as soon as there's a jam we're one-and-one merging). Maybe the best strategy for the traffic engineers would be to have the cones a half-mile before the speed change, or the other way around? Then you'd have stable-speed traffic merging. I assume that's been tried...
posted by nicwolff at 10:30 PM on April 25, 2005


This thread has been pretty thorough, but I haven't seen anyone exactly make this point [and this applies to congested traffic, not the Oklahoma turnpike at 1AM where merging amounts to a lane change]: you eager-beaver early mergers, seething at 3mph in one lane while we late-mergers drive on by towards the "zipper" -- you need to understand that we're not all being selfish. You work yourself into a slathering rage because you presume a selfish motive and feel slighted. But we just think you're being inefficient. Our business is probably no more important than yours, but we see no reason to emulate your self-righteous traffic-martyrdom by parking 5 miles out in one lane when the other is empty. Utilize both lanes, or you are just making it unfair for yourself!
posted by Tubes at 12:07 AM on April 26, 2005


Do you want a one-lane, one-mile long traffic jam or a two-lane, 1/2 mile long traffic jam? Personally, I will always let one car in, and I expect the same treatment. If everyone did that, it would not be a bad thing.

I always wait until the last minute to merge. Not because it gets me there faster, although it does, but because it is the most efficient utilization of the roadway, my time and resources. If others don't pick up on this, well...so be it.

I think the reason a lot of people immediately jump into the right lane and leave a big, giant slab of concrete unoccupied is because of peer pressure. "Everybody else is doing it; I guess I should, too."

It's like going to the grocery store and parking as far away from the front door as you can.
posted by wsg at 2:45 AM on April 26, 2005


You work yourself into a slathering rage because you presume a selfish motive and feel slighted. But we just think you're being inefficient.


I have always been an early merger (and prone to the angry refusal to let anyone to cut in front) but this thread has completely changed my mind. Now, how do I explain to all the people furiously sitting there watching me zip by that I'm not being a jerk but just following a strategy that traffic consultants actually recommend?
posted by CunningLinguist at 7:12 AM on April 26, 2005


This is partially local custom. When I lived out east, people used the zipper approach (wait until the last minute to merge). Here in Detroit, the custom (violated by selfish twits and people new to the area) is to merge as soon as you realize what is going on. I think the later leads to smoother and quicker merges.
posted by QIbHom at 9:13 AM on April 26, 2005


One problem with traffic is that it does not follow Bernoulli's Principle. When the apeture shrinks, it should move faster.

Actually, it does. Think: if two lanes of cars are approaching a bottleneck at 10 mph, then that means that cars past the bottleneck must be going at least 20 mph. So yeah, traffic speeds up as it passes a merge point or other bottleneck.
posted by kindall at 9:25 AM on April 26, 2005


Ever notice the big gaps in front of semis in the slow lanes where the truckers are letting in the late mergers?

Just a note on this. I do the same thing and I drive a car. It has nothing to do with letting in late mergers. The gap is not there for stopping distance, but rather to keep from having to stop. Leaving a gap of a couple car lengths lets cars in front of me come to a complete stop and start again while I only have to slow down, and don't have to switch gears. Being able to just speed up/slow down instead of clutch, brake, shift, gas, clutch, you can just let up off the gas a bit and speed back up once some space opens up between you and the one in front of you.

Also, I live in Portland and there is this nice hill going into Portland that I drive down everyday on the highway. I have to leave space in front of me for stopping distance because I drive an old car. One of these days one of the bastards that decided to cut in front of me as traffic is halting is going to end up with me in his trunk. And if I'm still able to walk I will ensure that person will be going to the hospital with me.

I stay to the right for as long as possible, but match speeds with traffic in the left lane, preventing the dickheads from speeding up.

I do the same thing, as well as truckers. On I-5, trucks do this all the time. When the Interstate bridge was cut from one to three lanes, truckers would parallel the lanes to make everyone wait their turn. The only ones that ever have a problem with it are the ones that think their time is some how more important than everyone else's.
posted by chrisroberts at 9:50 AM on April 26, 2005


QIbHom, the point of most of the arguments above is that the last-minute mergers are not (just) selfish twits, but are actually acting in the best interests of the overall traffic flow. The "local custom" of which you speak is counter-productive; it does not, in fact, lead to smoother and quicker merges, and it is to everyone's benefit not to follow it.
posted by MrMoonPie at 9:50 AM on April 26, 2005


MrMoonPie, that may be true in DC, but in Detroit, you will cause accidents merging at the last second. Or get frozen out by people who merged earlier, and are not going to let you in.

Overall traffic flow is not aided by emergency vehicles.
posted by QIbHom at 11:16 AM on April 26, 2005


Or get frozen out by people who merged earlier, and are not going to let you in.

There is always someone who will let you in. Not everyone is so petty.
posted by wsg at 11:57 AM on April 26, 2005


I wonder if anyone is still here.

Here's another example (if anyone is interested in thinking it through):

O You have three lanes of moving traffic. You see a sign that says the rightmost lane is going to merge with the middle lane some ways down the road. Which lane should you go in?

One would think the leftmost lane should move the fastest because it's not involved in the merge(r?) at all. It also seems most selfless to move quickly into the leftmost lane because it lowers the count of merging cars remaining in the other two. It thus is frustrating when, from the leftmost lane, you see the right lane going fastest up until the bottleneck point. Why is this?

(This is a different question than the one discussed endlessly above, right?)
posted by nobody at 1:40 PM on April 26, 2005


Here we see the underlying problem with so much driving in America: there is no agreed upon standard and people cannot co-operate with each other. The zipper technique is the safest and most efficient, provided everyone plays by the rules and doesn't try to exploit the situation (which almost always happens). If people are jumping the zipper, it quickly becomes a better idea to merge early and not try to fight it out later down the road. Often, in lighter traffic, early merging can be accomplished with less over-all speed reduction, thus making it the more efficient option. Again there is no standard here, so the multiple systems clash and cause more overall trouble. Much as the dangers of speeding are more about differences in speed rather than how fast you actually go, the mash-up that is daily traffic flow is the ultimate source of the problem. Generally the best you can do is be cautious and courteous and hope that others will as well.
posted by YurikoKinje at 7:23 AM on April 27, 2005


I merge fairly early when there's a spot available, then leave adequate room in front of me to allow people in the other lane to merge in as necessary. Ideally, if traffic isn't already near-stopped, the way to do it would be for everyone to slow enough to have space in front and in back and the lanes would "zipper" as has been mentioned.

I think the main problem with lane closings is that people go as fast as possible up until the last minute, then leave a minimum of space between themselves and other cars. I tend to think people drive too closely anyway, though.
posted by mikeh at 2:42 PM on April 27, 2005


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