Road Blocks: The Strange Things That Cause Traffic

The cause of a lot of the traffic congestion we battle everyday is pretty simple: too many people want to travel at the same time in the same direction to the same place, usually a job center. Since telework has been slow to replace the traditional workplace, it looks like this problem will be with us for a while.

For decades we have known about a way to deal with chronic congestion: levy tolls which vary depending on how crowded the road is. I’ve written about this here and here.

But pricing is not as well-suited for dealing with congestion related to unusual incidents, like breakdowns and wrecks. Even when these are relatively minor, incidents can start shock waves that cause serious amounts of delay as they ripple back through the traffic flow.

It’s hard to calculate precisely, but estimates I’ve seen suggest that incidents account for perhaps 50 percent of all roadway congestion. The most common incidents (80 percent) are breakdowns, stalls, flat tires, empty gas tanks, etc. In transportation lingo these are referred to as “disablements.” Anthony Downs, in his excellent book Still Stuck in Traffic, reports that overall these tend to generate about 15-30 minutes of delay per upstream car.

But incidents get far more varied and dramatic. In a well-done Los Angeles Magazine article on the mechanics of traffic congestion, Dave Gardetta chronicles many of the things that have caused major traffic tie-ups in the Los Angeles area. First, there are the spills—not just of things like oil and antifreeze, but of oranges, lemons, and even livestock. (L.A. has seen a traffic jam due to cows running loose on the freeway.)

(Matthew Philips)

Wild deer and coyotes cause traffic snarls, and domestic animals get into the act as well. July 5 tends to have an unusual number of animal-related traffic problems, as pets, spooked by the fireworks on the previous day, have a greater propensity to wander onto freeways.

Sadly, animal-related traffic jams are not all accidental. Sometimes litters of unwanted puppies are deliberately left on freeways to be run over. The California Department of Transportation often dispatches work crews to go out and collect trash bags of dead roosters the day after cockfights.

Even worse than animals dying on the roads are people. Freeways are a popular place to end it. People jump off bridges and overpasses, or deliberately drive into other cars or off the road; the frequency of highway suicides rises around Valentine’s Day. There are also higher rates of highway-related suicide in the days following some other well-publicized suicide. All of this can halt traffic.

And then there are the homicides. Deranged individuals have been known to drop bricks, bowling balls, pieces of the coastal mountain range, and even other people off overpasses.

Less tragic but considerably galling is the use of freeways as garbage dumps. Trash of all sorts has induced traffic jams, including but not limited to couches, chairs, refrigerators, and stoves. During the last week of December, discarded Christmas trees become a serious problem on the roads.

Mother Nature plays a role too. It may come as no surprise that rain, fog or snow can slow traffic, but even the position of the sun can cause tie-ups. Idyllic Los Angeles may not have blizzards or ice storms, but ironically our good weather can cause traffic jams; on clear days when there are spectacular views of the mountains, L.A. drivers get plenty of time to admire them as traffic slows.

Then there’s road construction, which is particularly maddening in Northern cities like my native Chicago, where snow, ice and the freeze-thaw cycle degrades the roadways. (Although I might add that my preferred conspiracy theory for the endless road construction while growing up—political corruption, maybe with the mafia thrown in somehow—got a boost when Rod Blagojevich purportedly conspired to authorize billions in senseless road building in order to extort cash from contractors.)

Finally, there are accidents, either between cars, between cars and pedestrians, or between cars and stationary objects. Overall, I’m happy to report that accident rates and severity in America have been falling for decades; in a future post I’ll look at by how much and why. However, there are still a tremendous number of crashes on American roads. Downs calculates that in a city the size of Philadelphia, Dallas or Boston there are roughly 300 accidents a day, including 20 per hour during rush hours. Downs’ numbers suggest that 40 percent of accidents block traffic lanes, causing roughly 45-90 minutes of delay per vehicle upstream.

Even the 60 percent of accidents that are quickly cleared to the side of the road can cause serious tie-ups. And this isn’t because the highway is blocked, but simply due to the fact that human beings have malleable morality and a ghoulish streak. Tell the truth: have you spent an eternity stuck in a gapers’ block, cursing the twisted Schadenfreude of the rubberneckers ahead of you, only to slow down yourself to gawk at the wreck when it’s finally your turn? Maybe we figure that since everybody ahead victimized us, maintaining the cosmic balance of justice in the universe demands that we in turn victimize those to come. Or maybe we simply have a morbid need to gape at the misery of our fellow humans.

Incident-related congestion will always be with us in some form. But there are ways we can cope with it. In the future, I’ll look at some ideas that can help keep barnyard animals and Christmas trees from ruining our morning commutes any more than actually having to go to work already does.



Amy Alkon

One thing that causes traffic backup is rude people who care nothing about anyone else on the road, like those who only pull up far enough in the left turn lane so they can get through the light, and never mind that people behind them have to be someplace. -Amy Alkon, author, "I See Rude People"


...not to mention those who, if there is a slight bottleneck, illegally take to the emergency lane and hurtle into the constriction. They convert a slight slowing of traffic into a stock still traffic jam

caleb b

Here is another conspiracy theory. The state of Oklahoma deliberately performs needless construction on I-35 to Dallas to prevent its citizens from traveling there on big weekends and spending money in Texas. Yes, I understand there will be many people on the road, but there is no need to close it down to ONE FLIPPING LANE FOR 40 MILES to fix a 10 foot stretch of road.

To me, the area around Ardmore has been down to one lane for 4 years now. FOUR YEARS! I could have build the entire road myself in four years.

One day I will become governor of Oklahoma with only two campaign promises:
1) Five lanes of highway, all the way to Dallas
2) Changing the law for 6point beer in OK, leaving Utah as the only 3.2 beer in the nation.


Along 118 I've seen trains, horses and tractor trailers in accidents fouling up traffic. Poor horse need a tow truck winch to drag it up on a flatbed. Poor horse thought it had freedom to gallop on its own at last only to get hit by a big ol' truck. Same with the tractor trailer, cables and winches all across the road.

Hey! Maybe I'm crazy, but aren't young women the WORST rubberneckers? That's what I've seen, over and over. Especially a group of young women, they will stop to literally drink in all the blood.


"they will stop to literally drink in all the blood."

Those are not young women: they are vampires. You should alert the appropriate authorities in your region to dispatch a staking team.

Ian M

I live in Ottawa, Ontario. It takes me less than 15 minutes to get home by bicycle (less than 3 miles). It takes over 20 minutes by car. I lock my bike at work. When I drive, I have to park a 10 minute walk away because it is the only parking available. Pretty easy choice but I do not like the dangers of biking in the rain or in the winter (and I am soft). I do love biking by cars in slow traffic and I can feel good that I am not driving that day.

I am a cyclist and I will admit that bicycles on the road can severly slow down traffic when there is no bicycle lane and by the way they ride. Many cyclists have no courtesy for cars. I see cyclists on a road that has an adjacent bicylce path in my city. Senseless and selfish. It is like they do it for spite.

Death Wish - I used to ride my bike to work in NewJersey.


On my way to work there is a stretch (about 10 miles) of one lane road that is extremely popular to bikers (note the "s", as in multiple, riding side by side, talking, totally ignoring the long line of cars behind them).


Most of my adult years, I have resolved to NOT rubberneck. When I finally get up to the wreck, I resolutely keep my eyes forward and tromp on the gas when the following-distance opens up - so I am part of the solution rather than the problem. However, caution (and in some states, the law) still dictates slowing down when there is a wreck and/or emergency vehicles ahead.


Hear hear.

"Tell the truth: have you spent an eternity stuck in a gapers’ block, cursing the twisted Schadenfreude of the rubberneckers ahead of you, only to slow down yourself to gawk at the wreck when it’s finally your turn?"

Uh, no. I scan the area directly in my path for bits of debris as well as EMT workers/vehicles, as well as rubbernecking jerks that are going 5 mph despite the open road in front of them and hordes of commuters who are running late for obligations behind them.

Maybe it's because the site of dead and injured people upsets me. As does the site of watching two idiots argue, holding up 45,000 commuters in the process, because of a $400 fender-bender (NC is the worst in this regard. Hey, lets take tens of millions of dollars of collective billable hours so this schmuck in a 1997 Volkswagen Jetta can have justice vis a vis his now-cracked tail light.)

Rubberneckers, next time you come across a wreck, please mind the workers, speed up, drive 'round, and console yourself with the fact that there'll be a wreck to rubberneck when you're a passenger in the future.



I would be interested in knowing how cell phone usage (talking and/or texting) has contributed to traffic congestion, either through increased incidence of accidents or general erratic driving behaviour, and associated traffic backups.


One issue I have is the governmental response (or lack thereof).

Whenever there is an accident, the troopers or highway departments act like they've never seen one before, and no organized traffic control is put in effect. Incredible amounts of time and fuel are wasted due to ineffectual accident planning. I know it takes work, but there should be written plans and alternate routes in effect for every mile of highway--so when something happens, they can act by plan, rather than haphazardly.

I have no date to support this statement, but I estimate that we could save millions of gallons of fuel every day if better highway traffic plans and controls were in effect to cover accidents, construction and the like.

Fat Man

I can think of at least two times that cash falling out of an Armored Car has caused traffic problems in my area.


We shared your comment from the pewlpit yesterday...

...we woke up to an inbox full of emails demanding to know where you live.

Please advise asap.


I factor I haven't heard discussed yet is the role of poor freeway design. In Seattle, for example I-5 was built with only two thru-lanes in each direction going through downtown, and also has a very poorly designed southbound I-5 to 520 interchange in which cars entering the freeway from NE 45th and 50th Streets have to cross four lanes of traffic in less than a mile in order to get on the 520 bridge.

Likewise, here in Beijing, where I am currently living (but not driving, thank god!), exits on the ring roads feature onramps BEFORE offramps, thus causing huge traffic jams as cars try to zig-zag through each other trying to get on and off the freeway.


Everybody complains about gapers, yet almost everyone is one. I am not, however.

When there's a roadside incident, there should be an extra guy to direct oncoming traffic to move the @#$% on.

Mike B

What always angers me is how poor the Continuity of Operations planning is for these strange events. State governments need to enshrine in law that after a traffic disruption the priority of the Emergency Services is the prompt re-opening of the road to traffic with all other factors being secondary. This means if there is a body or vehicle on the road you don't stand around for 2 hours drinking coffee while an investigation is carried out. The obstruction should be removed and traffic flow restored as quickly as possible. Police and safety officials rarely show any awareness of the extreme costs they are imposing on their community by keeping roads closed. If they were billed for the value of time wasted in investigations and other nonsense I doubt the problem would exist very long.

Moreover when there is a minor accident most people seem to forget that the driver's manual outlines that those involved need to clear the traffic lanes...not stop, get out and inspect the damage. Drivers that fail to make an attempt to clear the road should either be fined or summarily ruled to be both at fault.


Steve in CO

I know that everyone loves to rant about rubbernecking....but I have another theory. When there is an accident and sufficient traffic, consider what happens when the wreck occurs: people slow down or stop to avoid it. And if I slow down from 45 mph to, say 35, the car behind me must also slow, presumably to a rate slightly slower then me(at least for a moment). Push this back over 50 cars and you have a standstill. 2000 cars? Hour delay.10000 cars? You get the picture....