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deleted "Coined by transportation engineer and consultant Sam Schwartz, the" I know there is a claim this is so , see [1], I don't believe it, and believe the word appeared much earlier than 1980. Another reference has [2] it coined in 1971 in New York. New York, with its grid network is a logical place for the word to originate, more evidence here would help. Will reformat article. dml 13:49, 18 September 2005 (UTC)

FWIW, the OED cites 1980 as the earliest known usage. --Delirium 04:26, 25 December 2005 (UTC)

Contradiction: under "etymology," the first paragraph claims that the term wasn't extant before 1980, and the second paragraph claims that the term was coined in 1966. Which is it? Susan Davis 10:25, 10 December 2006 (UTC)

I would have thought "gridlock" was in use prior to 1980, as well, but I definitely would not know firsthand, having not even been born then; and everything coming up on a search indicates it is indeed from the 1980's. --Thisisbossi 15:53, 10 December 2006 (UTC)

I can't find any source to support the 1966 use of the word. Thus, I rewrote the Etymology section using the cited refs and removed the following lines (along with the 'contradict' tag):

The word ‘Gridlock’ entered the American lexicon in 1966.[citation needed] It owes its origins to the New York City transit strike of that year; where the intersections of Manhattan became so jammed with cars, that traffic on the entire island became hopelessly paralyzed. To alleviate the crisis, Mayor Lindsey took the extraordinary step of closing Manhattan island to all incoming traffic; and devoting all lanes on Hudson and East River crossings to outbound traffic only. There have been two transit strikes since then, but strict traffic control and vehicle occupancy rules have prevented a similar calamity.

--Mainstream Nerd 23:17, 18 March 2007 (UTC)


Deleted: Information on Domino's Pizza's former "30 minutes or less" guarantee. This is only vaugely (at best) related to the article

This should be merged with Traffic -- Mark J. 1000 UTC 24 May 06


I took out most of the "Reasons" section, since it was unsourced and came across as one person's best guess. I also added some references and removed the tag. --Mainstream Nerd 03:22, 20 March 2007 (UTC)

I can't claim to know the earliest date--but the guy who said 1966 is probably closest--it surely wasn't as late as 1980. Also the word itself is not related to the "traffic grid" except metaphorically. Rather, it's related to the fact that, to reduce occurrence, NYC took to painting a damn GRID at every intersection to provide a clear "NO-GO" into which intrusion would be INEXCUSABLE. Thus, it became more highly incumbent on a driver not to enter the grid on GREEN. Before the grids were painted, a blocking driver had the excuse that he couldn't see that there was no room on the far side of the intersection (and it was often true, as well). With the grid, each potential intruder could see a clear delineation on the far side into which room his vehicle could fit,should he risk entering. MUCH safer for pedestrians, too, especially of more aggressive type. A casual visitor to NYC would probably characterize both drivers and pedestrians as "aggressive" in comparison to other places. However, the painted grids also brought about a civility of both species (pedestrians and drivers) that would have been unimaginable back in "the old days." Taken to characterize a systemic problem (as the existing definitions so far had) is the viewpoint of a managing bureaucrat (or, perhaps, a traffic-conditions reporter) and is a perfectly valid definition (and certainly descriptive) but the term came into common usage when the grid pattern came to every intersection (I think they use something similar in the England called a "zebra."

New Jersey was ahead of its time (though not in cities) in using "traffic circles" so that flow never halted, as at an intersection. Except for newcomers, these were easily negotiable until sheer volume of traffic neccessitated a return to the conventional intersection.

And, since it "popped into my mind," another interesting road feature whose origin is lost in the dim recesses of prehitoric antiquity is the ubiquitous painted white line marking the outside edge of the roadbed. I'd been in almost every state by 1952 and the first place I saw that feature was in 1957--in Louisiana. It was explained as a help when driving at night or in their very frequent rain and fog--enabling the driver to see the road better without looking into the glare of oncoming headlights. Actually, it was another 15 years before it "caught on" and spread to nearly everywhere else. —Preceding unsigned comment added by (talk) 12:35, 31 January 2008 (UTC)


This recent picture might be a better illustration, since it is very closely matches the diagram :). --Thenickdude (talk) 01:44, 23 February 2008 (UTC)

If I understand the diagram correctly, it shows four seperate intersections. The picture only shows one. (talk) 12:32, 23 February 2008 (UTC)


The section on cause says it is caused by drivers entering an intersection, which they cannot clear. Has that really been proven? It is possible to construct cases, where a gridlock occurs even if all drivers act according to the rules. There would be gaps at all the intersections, but at a green light, not even the frontmost car can enter the intersection, because the way out is already blocked. Is there any study showing a noticable difference in the gridlock probability in the two cases? (I would expect a difference, but by how much?) (talk) 12:32, 23 February 2008 (UTC)

Perhaps in a closed system, where there is external outlet for vehicles at all, it would be possible to have gridlock without intersection blockages. However, a closed system would require more cars than there is available road space... for example, let's consider the state of Hawaii. The state has 2450 lane miles of roadway (1) (for this example, think of Hawaii as if it were a single island). Assuming a vehicle occupies 25 feet of length, it would take about 520,000 vehicles to occupy all of its roads. With a population of approximately 1,200,000, this is not entirely impossible; but unlikely. It firstly requires every 2.3 people as owning a vehicle and, furthermore, that they all take to the streets at the same time. A good chunk of that population is likely under 16, a senior who rarely drives, somebody whom walks, bikes, or takes transit, or someone whom is just too busy lounging about on the beach or surfing. It is theoretically possible to fail a system without blocking an intersection, but the likelihood of it occurring is not particularly high.
Think of it as one of those puzzles where you have a 4 x 4 card of 15 slider pieces and 1 gap, and you have to move around each piece until you get them in numerical order. That would be the same principle. If you have 16 sliders and no gaps: you can't move any pieces anywhere. However, the ratio of roads vs. cars does not have to be 1 to fail the system. It could require less cars to fail: perhaps there is an outlet which no one uses -- a side-street which a queued motorists refuses to take, wasting its capacity (like trying to solve a 4x4 puzzle without using the empty spot).
Also, it could still potentially operate successfully even at full occupancy. In this case, you would need a continuous loop of traffic which does not self-intersect. To visualise this, think of two separate rings which cross over each other at two points (this image has 3 rings: same result, but just easier to think of 2). In this situation, every vehicle on each ring is destined for a location on that same ring. Now, your gap in the 4x4 puzzle is the same thing as the gap at the intersections. You move all the vehicles in one ring at the same time; then you move all the vehicles in the other ring at the same time -- always maintaining the gap at the intersections. You don't have to move every vehicle at the exact same time, as of course in reality people wouldn't do that -- the first car moves, then the second, then the third, and so on. You just have to wait until the intersection clears again before you run the next ring.
This can be expanded to multiple rings, whether they be configured in a chain or in an overlapping arrangement. Consider this, where you can run each ring one at a time; or this, where you can run the whole set in three phases: the top-right ring, the bottom-left ring, and then both the top-left and bottom-right rings.
Note that the previous example does not work if a ring self-intersects (like a figure 8), as the first vehicle to block the intersection will have failed it because now the other side can't move; and on the other hand, if both vehicles do not block the intersection, then it still fails because no one moves. This, unfortunately, is a more realistic scenario: the above paragraph's example makes a BIG assumption to imagine ourselves being destined for a location on the same ring upon which we originated. In reality, our rings are all highly interconnected and self-intersecting.
--Bossi (talkgallerycontrib) 18:03, 23 February 2008 (UTC)
Imagine a situation where you have a ring, and a number of cars that intend to enter the ring at different points and drive along the ring for some distance before leaving it again. If enough cars are entering at around the same time, the ring could be completely filled with cars before the first one makes it to the place where it would leave the ring. Kasperd (talk) 18:20, 23 February 2008 (UTC)

New Image[edit]

Would this image be appropriate? Gridlock Image Johnthefreelancer (talk) 00:55, 13 May 2008 (UTC)

Historical Events[edit]

While it mentions the less precise uses for the term, this article is very specifically about the type of gridlock caused by intersection blocking or close freeway ramps, not just traffic jams in general. None of the three examples seems to be particularly relevant to the rest of the article, and they should probably be moved to Traffic jam (the China and Brazil paragraphs are already there). — Preceding unsigned comment added by Andthendougsaid (talkcontribs) 16:16, 28 August 2011 (UTC)

  • I agree: while the article makes a clear distinction between gridlock and other types of congesion (i.e. examples of demand exceeding maximum throughput), this is not clear for the historical events sections, and by the way neither for the Toronto example. I support removing examples that are not specifically and explicitly related to gridlock phenomena. KKoolstra (talk) 12:08, 6 October 2015 (UTC)

Roadway air dispersion modeling[edit]

The "See also" section links to Roadway air dispersion modeling. I don't quite see how that is related; was the intent to say that most roadway air dispersion models take gridlock as an input variable? Or is it okay for me to remove the link? --SoledadKabocha (talk) 19:13, 20 November 2012 (UTC)

Left turn gridlock[edit]

Another form of severe congestion that can be as bad as gridlock and therefore might be called gridlock, although as explained here does not fit the traditional meaning is what I call left turn gridlock. Basically, it's where when road A with very heavy traffic gets the red light, the next thing is for road B to get left turn arrows. If the traffic that made the light on Road A is slow enough, the left turners and subsequent right turners (when road be turns green after the arrows) can fill all the space that appeared on road A, beyond the light, after turning red. This is not purely theoretical. This occasionally happens and often nearly happens on such roads as US 1 in Florida over a 10-mile stretch from the southern terminus of Interstate 95 to about Ludlam Road. B137 (talk) 15:53, 24 December 2014 (UTC)