Late to merge
I think people should have ’strong opinions weakly held’. I also think my debate/critical reasoning skill are getting weaker as I get older. So it seems like good practice to argue strongly for a weakly held opinion.
There is a stigma against people who merge late on roadways. Popular behavior dictates that one should vacate the closing lane as soon as signs announce that the lane closes in a few miles. I think those arrogant drivers rushing past rows of idle traffic are actually behaving efficiently and in accordance with Kant’s moral imperative. Those who merge at the first sign are slowing everyone down with their conformity.
Merging late is more efficient because it minimizes the duration of time when traffic is constrained to one lane. Having a 50-foot stretch of one-lane road does not slow down traffic as long as the flow of traffic is less than one car per 50 feet of road. But if all traffic merges miles in advance, 1 car/50 ft. of road is enough to cause backup. Merging late maximizes the use of available road, which alleviates bottlenecks.
Merging late concentrates the location where drivers switch lanes. This avoids drivers slowing down further while they negotiate who’s changing lanes. Drivers should understand that alternating lanes in the optimal way to merge two lanes into one, and if people use all available roadway, the lanes will be equally full at the point of merging. Since less negotiation is needed, drivers won’t need to slow down as much in order to be cautious of unexpected merging.
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by Aaron Suggs on Tuesday, December 19th, 2006 at 10:51 pm and is filed under Nothing in particular.
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February 5th, 2007 at 11:04 am
Totally late comment here, but better late than never, right?
In New Zealand, they have these big signs telling people to “merge like a zipper,” and you’re encouraged to just merge at one point. I also totally agree with you that it’s more efficient to have everyone merging at one point in smooth motion (tho I used to be the considerate “merge ASAP to keep people from stopping,” until I realized that people stop more with unpredictable merging). That way, you’ve got to slow down, but you ideally should not have to stop. I’ve even begun to extend this idea of not stopping to all stop and go traffic — seems like it would be more efficient for everyone to slow down and crawl rather than let a gap open, gun it, slam on brakes, and repeat ad infinitum.
so, just another voice that agrees.
February 5th, 2007 at 1:20 pm
I was just re-reading you’re “Late to Merge” blog entry and couldn’t resist responding. With some counterpoints …
First, it’s not the length of the bottleneck that matters. It’s the state change (going from N-lanes down to one) immediately leading up it that causes the problem. As long as there are enough cars on the road that a state change is required (i.e. there are cars occupying more than one lane) than drivers will have to take pretty much the same action, regardless of how long the bottleneck itself is.
Which leads to the next point: For any given situation (bottleneck width, # of drivers, etc.), the time required for drivers to jockey into a steady-state position that allows them all to pass through is more or less constant. With the “merge late” policy the distance they have to jockey for position is shorter, which means that to have enough time to jockey, everyone has to slow down. Conversely, a merge-early policy maximizes the speed at which this jockeying can take place so that by the time the cars encounter the bottleneck, they are passing through it faster.
There is also the philosophical question of what constitutes the “greater good”. Even assuming the merge late policy works better, it forces drivers to operate at their maximum capacity for processing events - i.e. at maximum stress level. This is further exacerbated by the one-handed nature of driving this involves (the other hand being required for gesticulating angrily at the other drivers!)
Oh, and one final note. Even if 99% of drivers on the road are merge-early’ers who can achieve a steady state well in advance of the bottleneck, that one merge-late driver disrupts the whole system again at exactly the wrong point, right before the bottleneck, such that it requires everyone to pretty much start the jockeying process all over - in effect making them all merge-late’ers.
Which, I guess, argues in favor of merge-late. Not because it’s the better policy, but because it is inevitable. Thus, the philosophical greater good emerges when the merge-early’ers use this exercise to raise their spiritual awareness by accepting the merge-late’ers for the insensitive, egocentric bastards they are. And the merge-late’ers… well… they get to their morning status meeting on time, which is probably it’s own form Karmic justice.
;-)
[Author’s disclaimer: I am by nature a merge-late’er, but I strive for merge-early awareness.]
February 5th, 2007 at 1:22 pm
Robert,
I remember reading a great article with animated models and such written by a researcher at the NHTSA or something…but I can’t find the link.
Anyway, I grant that my argument was scant on evidence, and here’s another supporting argument, again with scant evidence: http://uwnews.washington.edu/ni/article.asp?articleID=25011 (I wish that article said whose research the article was summarizing)
I disagree with your point below that the time for a driver to jockey for position is more or less constant. It takes longer to jockey for position when there’s a half-mile stretch of road on which people are merging than when there’s a single point of merger. If drivers filled both lanes up to the merge point, then alternated having a car from each lane proceed on the merged lane, the time spent “jockeying” would be less…it would hardly be jockeying at all, since there’s no aggression or submission to get in to a spot–people are just following the algorithm.
February 5th, 2007 at 11:44 pm
Seems to me that you could think of the jockeying time this way –
at a four way stop, there is a predictable course of action to take, so you can get through fairly quickly with not too much stopping. If the stop signs weren’t there, you wouldn’t know who should go first. It would likely take more time as people attempt to communicate.
The merge lane is similar. If every car merges at one point, you simply follow the first one car, then the other rule. Simple, not too much fuss, and with minimum stoppage/slowdown once people are well versed in how to do it.