A mismatched, jammed zipper of rage.
September 7, 2010 11:23 AM Subscribe
When losing a lane on a highway, what is the proper place to merge?
For instance, when a two-lane highway loses a lane due to construction, most people seem to start getting over into the open lane as soon as there are "Lane Closed Ahead" signs. This seems to slow traffic down, though- wouldn't the proper place to merge be at the actual lane closure point? This is an issue of contention between me and some friends- they get over right away, but I think you should merge at the last second, like a zipper.
Is there a "correct" way to merge?
For instance, when a two-lane highway loses a lane due to construction, most people seem to start getting over into the open lane as soon as there are "Lane Closed Ahead" signs. This seems to slow traffic down, though- wouldn't the proper place to merge be at the actual lane closure point? This is an issue of contention between me and some friends- they get over right away, but I think you should merge at the last second, like a zipper.
Is there a "correct" way to merge?
Ideally, everyone would merge at the point at which the lane stops; otherwise, yes, this does slow things down. (There's an explanation of this pretty early in Tom Vanderbilt's very very excellent book Traffic.)
Unfortunately, we are idiots when we drive, and think that merging early is virtuous. We then punish late mergers by not allowing them in, thereby making late-merging unattractive, even though it would be faster.
posted by punchtothehead at 11:27 AM on September 7, 2010 [8 favorites]
Unfortunately, we are idiots when we drive, and think that merging early is virtuous. We then punish late mergers by not allowing them in, thereby making late-merging unattractive, even though it would be faster.
posted by punchtothehead at 11:27 AM on September 7, 2010 [8 favorites]
Racing past cars to get to the end point and then thinking you'll be let in is not zippering, if that's the strategy your friends are objecting to.
posted by sageleaf at 11:34 AM on September 7, 2010 [2 favorites]
posted by sageleaf at 11:34 AM on September 7, 2010 [2 favorites]
the proper place to merge is one that doesn't require you to slow down.
posted by rhizome at 11:47 AM on September 7, 2010 [6 favorites]
posted by rhizome at 11:47 AM on September 7, 2010 [6 favorites]
Racing past cars to get to the end point and then thinking you'll be let in is exactly the most beneficial method for everyone to follow, if you believe the well-researched and thoroughly-reasoned aforementioned Traffic, the fact that it hurts sageleaf's feelings notwithstanding.
posted by MrMoonPie at 12:02 PM on September 7, 2010
posted by MrMoonPie at 12:02 PM on September 7, 2010
Your first assumption isn't exactly true. The "zipper" method is more efficient in heavy congestion, the early-merge is better in lighter traffic. It's situation dependent.
If you're already stop-and-go, then sure, stopping to zipper is more effective. If you're slowing only some, then merge when safe, and go right on through.
The worst is the mix of both. 99% of people merge early, are cruising along, and then suddenly you have to brake because someone decided to zoom past ~200 cars and cut you off because they waited until the last second to merge.
posted by Tooty McTootsalot at 12:06 PM on September 7, 2010 [2 favorites]
If you're already stop-and-go, then sure, stopping to zipper is more effective. If you're slowing only some, then merge when safe, and go right on through.
The worst is the mix of both. 99% of people merge early, are cruising along, and then suddenly you have to brake because someone decided to zoom past ~200 cars and cut you off because they waited until the last second to merge.
posted by Tooty McTootsalot at 12:06 PM on September 7, 2010 [2 favorites]
By far the best way (in relation to total traffic flow) is for both lanes to merge at roughly the latest safe point where the two lanes are travelling at similar speeds. Ideally, this would be in a relatively fair manner (ie no-one jumping ahead 20 cars). It does not need, in any way, to be one after the other - effective traffic flow is bigger than any one individual's claim for consideration and minimal disruption to each car's speed in the merge is the crucial factor. NOT where it ends up in the merged traffic in relation to the cars it was behind before the merge.
The 'fairest' point as presented in that other thread, where people think they are all getting a fair go (even in countries that don't line up or queue as part of their culture, apparently), is supposedly to go one after each other like a zip at the termination point of the lane (thus preventing anyone stealing through a few cars and getting the best by 4 car lengths or so). However, this is usually the most damaging for traffic flow as a whole, as the backing up of the merging lane slows traffic in both lanes and screws everyone up by dropping the average speed and starting the concertina effect of accel/decel much sooner than it needed to be. In that example, everyone back of the merge point gets screwed (but, apparently crucially, EQUALLY screwed) by an inefficient traffic flow. Yes, you (AN Other driver) may have got through before that arsehole in the flash red car that tried to get ahead of you, but everyone behind you had to brake while you blocked him. You've probably created 5 minutes of delay further back in traffic just from that one move. Seriously. Maybe more time than that. One day, you'll be further back in the traffic jam and that will come back and haunt you.
In short, if people have to slow down to allow anyone else to merge (or even worse, brake) you've already screwed everything up and traffic is slower than it could have been. Being one or two car lengths further ahead in screwed traffic and being happy with it shows you spectacularly missed the point.
What amazes me is that some people equate 'fair' with 'each car lets another car in' and try and convince themselves that this is the best solution/least disruptive to their journey time. This is, of course, complete rubbish as the single biggest factor in how much the lane closure affects their journey time isn't the 20 or 60 (or even 100) feet from letting 1 or 4 cars in or whatever, but how much the speed of traffic is disturbed by the merging process. It says much more about social dynamics than any accurate traffic flow theory - my car is more expensive than yours, so you have to wait. If you create a merging situation where (by cramping the traffic into the end of the closing lane) there is a high speed differential between the two lanes (and thus a lower average speed for the post-merged traffic) then you've held your head high as 'fair' in a bizarre and senseless manner. If you let in 8 cars more than the guy behind you, your difference in journey time is practically immeasurable - you will be there 8 car lengths later - big whoop. If you dropped speed keeping 'your turn', though, you did much more damage to your arrival time and that of everyone behind you.
The only thing that will reduce the delay of a traffic merge is to keep the speed of both lanes (and the joined one) as high and as constant as possible. Merging in plenty of time allows this to happen, and even keeping the merged traffic faster by 1mph (ie the nest loss in average speed of both lanes is 1mph less) as a result will mean a much smaller delay to your travel time even if you let 10 people in to allow you to maintain this speed. People that believe that 'one from column a and one from column b' merging is the crux of the matter know nothing of fluid dynamics or traffic flow.
Also, if people merged less pedantically and selfishly, then everyone behind them (which may be you at some point) will get through faster. The reason truck drivers block lanes off and hold speed together and merge early is that they drive all day and every day and have seen the significant and detrimental effect of last minute-joining idiots. It affects their bottom line enough for them to make a point at each road works, yet no-one in cars seems to think it matters as long as they get in front of the car next to them.
posted by Brockles at 12:07 PM on September 7, 2010 [3 favorites]
The 'fairest' point as presented in that other thread, where people think they are all getting a fair go (even in countries that don't line up or queue as part of their culture, apparently), is supposedly to go one after each other like a zip at the termination point of the lane (thus preventing anyone stealing through a few cars and getting the best by 4 car lengths or so). However, this is usually the most damaging for traffic flow as a whole, as the backing up of the merging lane slows traffic in both lanes and screws everyone up by dropping the average speed and starting the concertina effect of accel/decel much sooner than it needed to be. In that example, everyone back of the merge point gets screwed (but, apparently crucially, EQUALLY screwed) by an inefficient traffic flow. Yes, you (AN Other driver) may have got through before that arsehole in the flash red car that tried to get ahead of you, but everyone behind you had to brake while you blocked him. You've probably created 5 minutes of delay further back in traffic just from that one move. Seriously. Maybe more time than that. One day, you'll be further back in the traffic jam and that will come back and haunt you.
In short, if people have to slow down to allow anyone else to merge (or even worse, brake) you've already screwed everything up and traffic is slower than it could have been. Being one or two car lengths further ahead in screwed traffic and being happy with it shows you spectacularly missed the point.
What amazes me is that some people equate 'fair' with 'each car lets another car in' and try and convince themselves that this is the best solution/least disruptive to their journey time. This is, of course, complete rubbish as the single biggest factor in how much the lane closure affects their journey time isn't the 20 or 60 (or even 100) feet from letting 1 or 4 cars in or whatever, but how much the speed of traffic is disturbed by the merging process. It says much more about social dynamics than any accurate traffic flow theory - my car is more expensive than yours, so you have to wait. If you create a merging situation where (by cramping the traffic into the end of the closing lane) there is a high speed differential between the two lanes (and thus a lower average speed for the post-merged traffic) then you've held your head high as 'fair' in a bizarre and senseless manner. If you let in 8 cars more than the guy behind you, your difference in journey time is practically immeasurable - you will be there 8 car lengths later - big whoop. If you dropped speed keeping 'your turn', though, you did much more damage to your arrival time and that of everyone behind you.
The only thing that will reduce the delay of a traffic merge is to keep the speed of both lanes (and the joined one) as high and as constant as possible. Merging in plenty of time allows this to happen, and even keeping the merged traffic faster by 1mph (ie the nest loss in average speed of both lanes is 1mph less) as a result will mean a much smaller delay to your travel time even if you let 10 people in to allow you to maintain this speed. People that believe that 'one from column a and one from column b' merging is the crux of the matter know nothing of fluid dynamics or traffic flow.
Also, if people merged less pedantically and selfishly, then everyone behind them (which may be you at some point) will get through faster. The reason truck drivers block lanes off and hold speed together and merge early is that they drive all day and every day and have seen the significant and detrimental effect of last minute-joining idiots. It affects their bottom line enough for them to make a point at each road works, yet no-one in cars seems to think it matters as long as they get in front of the car next to them.
posted by Brockles at 12:07 PM on September 7, 2010 [3 favorites]
My anecdata suggests that staying in (or getting into) the lane that is ending until it ends and then merging back is the most time-efficient option.
posted by clicking the 'Post Comment' button at 12:11 PM on September 7, 2010
posted by clicking the 'Post Comment' button at 12:11 PM on September 7, 2010
I never personally got the point of trying to milk the merging lane for as long as possible. More often than not you get to the end and you aren't being let through. The zipper works just as well if it's early, except for the entitled pricks that decide that's not good enough and decide to zip in front of the line, trying to get ahead of early mergers. That just breaks everything.
If you wait till the last possible moment, you will likely come to a stop and then will need to try and force your way in to the merged lane. That's terrible for everyone involved. If you merge early, you merge without stopping, at the first opportunity, and traffic keeps going. That's better for everyone, and I see a hell of a lot more consideration from the other lane to let people merge early and safely, rather than late as hell after passing by many merging opportunities, just for the powerful feeling of getting ahead of everyone else.
I'd love to see what Traffic has to say about it, and what assumptions it has that do not translate to real world driving. I don't care how well researched or thoroughly-reasoned it is, merging late is a goddamn clusterfuck in the real world, and merging early is both easier and safer.
posted by splice at 12:12 PM on September 7, 2010 [3 favorites]
If you wait till the last possible moment, you will likely come to a stop and then will need to try and force your way in to the merged lane. That's terrible for everyone involved. If you merge early, you merge without stopping, at the first opportunity, and traffic keeps going. That's better for everyone, and I see a hell of a lot more consideration from the other lane to let people merge early and safely, rather than late as hell after passing by many merging opportunities, just for the powerful feeling of getting ahead of everyone else.
I'd love to see what Traffic has to say about it, and what assumptions it has that do not translate to real world driving. I don't care how well researched or thoroughly-reasoned it is, merging late is a goddamn clusterfuck in the real world, and merging early is both easier and safer.
posted by splice at 12:12 PM on September 7, 2010 [3 favorites]
My anecdata suggests that staying in (or getting into) the lane that is ending until it ends and then merging back is the most time-efficient option.
It's the most efficient option for your own personal self-satisfaction, as you rush ahead of your fair spot, passing people who are merging safely, in order to get to the front of the queue and force your way in when others don't want to let you merge, all so that you can be one or two cars ahead (YAY! TIME EFFICIENCY!) while making the merge spot less safe for everyone and screwing everyone behind you by forcing them to stop to let you in.
posted by splice at 12:14 PM on September 7, 2010 [5 favorites]
It's the most efficient option for your own personal self-satisfaction, as you rush ahead of your fair spot, passing people who are merging safely, in order to get to the front of the queue and force your way in when others don't want to let you merge, all so that you can be one or two cars ahead (YAY! TIME EFFICIENCY!) while making the merge spot less safe for everyone and screwing everyone behind you by forcing them to stop to let you in.
posted by splice at 12:14 PM on September 7, 2010 [5 favorites]
Merging late is ideal when every driver is working cooperatively. Everyone is traveling the same speed, and there is room to merge at the last possible moment without stopping (or even slowing down.)
This breaks down in real world situations. For example, say everyone is traveling 45 miles an hour in both lanes. What happens when the car about to merge at the last possible moment is blocked from merging? Crash, bam, boom - hope you weren't working road construction that day.
posted by m@f at 12:22 PM on September 7, 2010
This breaks down in real world situations. For example, say everyone is traveling 45 miles an hour in both lanes. What happens when the car about to merge at the last possible moment is blocked from merging? Crash, bam, boom - hope you weren't working road construction that day.
posted by m@f at 12:22 PM on September 7, 2010
My anecdata suggests that staying in (or getting into) the lane that is ending until it ends and then merging back is the most time-efficient option.
If you can do that without affecting anybody else's speed, then bully for you.
posted by rhizome at 4:12 PM on September 7, 2010
If you can do that without affecting anybody else's speed, then bully for you.
posted by rhizome at 4:12 PM on September 7, 2010
Merging in plenty of time allows this to happen, and even keeping the merged traffic faster by 1mph (ie the nest loss in average speed of both lanes is 1mph less) as a result will mean a much smaller delay to your travel time even if you let 10 people in to allow you to maintain this speed.
This is what I don't get. In every situation like this I've been in, the way I would let people in ahead of me would be by slowing down. How on earth would slowing down block people from merging?
posted by Deathalicious at 10:18 PM on September 7, 2010 [1 favorite]
This is what I don't get. In every situation like this I've been in, the way I would let people in ahead of me would be by slowing down. How on earth would slowing down block people from merging?
posted by Deathalicious at 10:18 PM on September 7, 2010 [1 favorite]
I like the Traffic Waves guy. He has some ugly design, but check out his animated traffic samples.
posted by Sallyfur at 1:57 AM on September 8, 2010
posted by Sallyfur at 1:57 AM on September 8, 2010
Deathalicious: "This is what I don't get. In every situation like this I've been in, the way I would let people in ahead of me would be by slowing down. How on earth would slowing down block people from merging?"
From what I can decode from the passive-voice disaster you quoted, I believe the answer to your question is not that slowing down blocks people (though it can), but that blocked mergers slow everybody else down.
If you're a late merger who just so happens to wind up at the end of the lane before moving over and you also happen to have another car next to you, you have to slow down lest you wind up in the shoulder. Now you're moving slower and still have to merge. What of the people in the next lane behind you? They have to slow down to let you in, making your lazy merge a problem for multiple people and slowing traffic down in general.
posted by rhizome at 11:42 AM on September 8, 2010
From what I can decode from the passive-voice disaster you quoted, I believe the answer to your question is not that slowing down blocks people (though it can), but that blocked mergers slow everybody else down.
If you're a late merger who just so happens to wind up at the end of the lane before moving over and you also happen to have another car next to you, you have to slow down lest you wind up in the shoulder. Now you're moving slower and still have to merge. What of the people in the next lane behind you? They have to slow down to let you in, making your lazy merge a problem for multiple people and slowing traffic down in general.
posted by rhizome at 11:42 AM on September 8, 2010
This thread is closed to new comments.
posted by Cat Pie Hurts at 11:25 AM on September 7, 2010 [1 favorite]