The Science of Traffic Jams – If Everyone Drove Like Me…

o-traffic-jam-facebookIf there is anything I hate worse in this world, it is traffic jams.  I consider myself as a polite, empathetic, safe and aware driver.  I signal when I turn, check my blind spots, let people in and clear my license plate and lights when it snows.  However, I do not have the patience for drivers who have absolutely no politeness, don’t use their turn signals, drive slow in the fast lane, hit their brakes when they don’t need to, text on their cell phones or generally don’t pay any attention.  When I drive, my attention is on the road, not on some text message I just received!

So I was driving along C-470 one day (a loop that goes around parts of Denver) and as I came to the crest of a hill, I noticed an unending string of brake-lights in front of me.  I was forced to slow from 65 to a crawling 15 and eventually to a full, complete stop.  I didn’t have anywhere to be at a certain time, so I settled in and waited.  As my mind began to wander, as it often does during long pauses in my commute, I pondered the question of what causes a traffic jam?  Thus began the workings of a new blog post!

So what does cause a traffic jam?  Construction, an accident, Occupy Denver protesters, too many cars and not enough road; the list can go on.  For the remainder of this post, I will focus on issues that cause traffic jams, the problem and the solution.

Issue Number One – The Construction Bottleneck

road-construction2       Problem: The Early Merge

Most drivers are inherently idiots when it comes to merging.  Usually whenever people see the “lane closed ahead” sign in a construction zone, they slow down too quickly and merge onto the lane that will continue on through the construction area.  This driving habit can lead to abrupt and unsafe lane changing, accidents and of course road rage (including but not limited to any combination of middle finger flipping, insulting  body language, horn honking and/or transference – blaming it on someone who had nothing to do with the traffic jam, like their in-laws) (Plumer, 2013).

Most motorists feel bad about merging at the last moment.  They feel that the cars in the continuing lane have first-born rights or tenure because they were there first so most drivers are more likely to merge to the open lane whenever they see the construction sign.  As a result, this causes a “bottleneck” (MnDot, 2012).

            Solution: The Zipper Merge

wawdharStudies have revealed that the hazards of early merging decline when drivers stay in their respective lanes until they arrive at the exact designated merge area and then take their turns merging in a “zipper” technique into the open lane.  This is called a “zipper merge” and yes, it is an actual term used by the department of transportation.  “Zipper merging” benefits singular drivers as well as general traffic as a whole.  However, in order for a “zipper merge” to become successful, it requires the participation and adherence of all drivers.  Because most drivers have never heard of the “zipper merge” (including me until now) and no one driver behaves alike, most “zipper merges” are unsuccessful (MnDot, 2012).

Tom Vanderbilt

Tom Vanderbilt, a leading journalist, author, blogger and expert in traffic science stated, “My main take-away from this is that the individual driver can often not understand the larger traffic system,” (Plumer, 2013)

If you are still perplexed on this, you might be asking, “So am I supposed to merge late?” And the answer is, “Yes!” As soon as you see the “lane closed ahead” sign and a bottle neck is forming, don’t move over just yet.  Remain in your lane until you get to the merge area.  Then, if it all goes smoothly (and nobody is following too closely), drivers in the continuing lane should take turns letting drivers in the merging lane move over.

Don’t worry about being “nice”.  Sometimes you need to be a little “aggressive” with your driving and set an example for other motorists in order to make traffic flow smoother.  Now that you know this little trick, you can teach it to other drivers!  The main point of this is to always move over when it’s safe to.  Don’t shove your way in front of a car if they’re not going to let you in.

Issue Number Two – The Phantom Traffic Jam

            Problem: Braking Too Much

66fceaabf64b3e034a0f6a706700925bWhenever people can see clearly, traffic moves
along smoothly for the most part.  However, it seems that whenever there are visual limitations, drivers hit the brakes, which causes the car behind them to do the same and so on.  It turns into a continuous chain reaction that can cause a traffic jam that can stretch for miles.  There can be any number of visibility issues: fog, rain, snow, sun glare, etc.  Another example is if a diesel truck merges onto the highway, it can impact the traffic behind it.

Mathematicians from the University of Exeter in England have developed a computer model that explains traffic flow.  They call it the “Exeter Model”.  While slowing down below the flow of traffic because of a slowly moving vehicle or low visibility, a motorist, in turn, may cause the vehicle behind them to slow down even more and as a result, the next car back has to lower its speed even further (University of Exeter, 2007).

The effect of this one driver is that a few miles back, traffic would be at a stand-still, with motorists unaware as to why traffic has stopped.  The traffic jam turns into a chain reaction that moves towards the rear of traffic creating a supposed “backward travelling wave”, in which commuters can experience many miles “upstream”, several minutes after the original driver stepped on their brakes (University of Exeter, 2007).

gabor_oroszDr. Gábor Orosz of the University of Exeter explained, “As many of us prepare to travel long distances…, we’re likely to experience the frustration of getting stuck in a traffic jam that seems to have no cause.  Our model shows that overreaction of a single driver can have enormous impact on the rest of the traffic, leading to massive delays.” (University of Exeter, 2007)

The front of the congestion might be moving along at 15 mph, the middle might be at a stand-still and the end of the line may be traveling at 25.  Traffic all depends on how quickly a motorist decides to brake or accelerate and that is the frustrating part.  No one driver has the same habits and behavior.  You might be someone who likes to be on the move and takes an opportunity when you see it.  “There’s an opening!” and off you go!  However, the slow-poke in front of you might be totally opposite.  They don’t take risks.  They drive leisurely instead of strategically.  They throw their brakes on almost as a habit.  And as with most situations in life, when people with different behaviors, backgrounds, habits and practices get thrown into the same line, usually the late-for-work, impatient, pushy, irate, restless, eager, irritable drivers end up behind the usually older, slow, easy-going, laid-back, relaxed drivers.

            Solution Number I: The Exeter Model

Frustrated commuters and policy-makers have always been baffled as to why traffic jams like this occur.  Most have concluded that it was due to the large amount of traffic.  Even though this is partly true, the main issue of the theory deals with the smoothness of traffic flow.  According to the model, heavy traffic does not necessarily result in blockage.  There are times when excessive traffic can run smoothly.  The Exeter Model includes the time-delay in a motorist’s response, which results in drivers braking more heavily than they needed to if they had recognized and responded to a problem ahead moments before (University of Exeter, 2007).

University of Exeter Engineering Department

Dr. Orosz continued, “When you tap your brake, the traffic may come to a full stand-still several miles behind you.  It really matters how hard you brake – a slight braking from a driver who has identified a problem early will allow the traffic flow to remain smooth.  Heavier braking, usually caused by a driver reacting late to a problem, can affect traffic flow for many miles.” (University of Exeter, 2007)

The researchers at Exeter have plans to establish an additional model that can be utilized in vehicles furnished with new electronic accessories, which can decrease over-braking as an outcome of slow response (University of Exeter, 2007).

            Solution Number II: The Berthold Horn Technique

 What causes these backups anyway?  Berthold Horn, a professor of computer science and engineering at MIT, might have found a way to put an end to at least one kind of really annoying traffic jam (Palca, 2013).

bkph_andorra2_trimmed_stretched_smlDuring an interview with NPR, Horn explained his solution, “There’s no accident.  There’s no one speed-trapping, and you’re puzzled.  What’s going on?  A typical case would be someone slams on the brakes just for a short moment.  The car behind them is forced to slam on the brakes and so on back upstream.  It’s like a wave flowing backwards.

“People who study this talk about chaotic systems and positive feedback, but the practical consequences are that the amount drivers have to slow down increases the further back you are from the original incident.  There may be someone who is forced to actually stop.” (Palca, 2013)

Horn believes he might have a way to even out that wave and keep traffic flowing steadily.  His technique concerns not only being aware of the driver in front of you but also the one behind you.  It may seem unreasonable but according to his estimates, this method of driving can prevent these phantom traffic jams (Palca, 2013).

“The easiest way to think about it at first is you’re trying to maintain a distance Highway-Signhalfway between the car ahead and the car behind,” Horn continues, “Doing that will smooth out the traffic.  Now to make the scheme really work, you need cars that can do the forward and backward monitoring on their own and make the necessary adjustments automatically.  There would be some benefit if lots of people kept track of their spacing using their rear-view mirrors and didn’t tailgate.  Once I came up with this idea, I changed my own driving behavior.” (Palca, 2013)

Horn said that he actually measured a small progress during his commute as a result of practicing this newly found method (Palca, 2013).

Issue Number Three – Too Many Drivers, Not Enough Road

            Problem: Rush Hour

imageThere are certain times of the day when only a maniac would get on the highway and go for a nice drive.  Those times are usually when every normal person goes to work, eats lunch and comes back from work.  Between 7:00 and 9:00 am, noon and between 4 and about 7:00 pm are normal rush hour times.  I am not one of those “normal” people, so my commute to work is rather traffic free, thankfully.

There are also those times when normal work people have holidays.  During these times, they would rather be anyplace other than home, so they embark upon the highways of America and go places that they usually do not.  This is called “going on vacation”, “vaca”, “going on holiday”, “sabbatical”, “R and R” or “the long weekend”.  It is during these times that traffic jams may also occur.

The issue with rush hour is mostly that there are too many cars on the road and not enough road to accommodate the cars.  Simply put, if there isn’t enough space, the cars must drive slower.

            Solution: Public Transportation, Walk or Stay Home

public_transport_vs-_car-650x0_q85_crop-smartOne research study that followed Boston motorists during rush hour discovered that if only one percent of the drivers were removed from the road, there would be an eighteen percent improvement in the flow of traffic (Plumer, 2013).

How might this one percent of drivers be removed you ask?  Does the city you live in have a bus system?  A Subway (not that Subway – the one underground!)?  A Lightrail system?  A trolley?  A taxi, tram, ferry, cable-car, streetcar or carpool system?  Regardless the method of public transit, there is usually an option other than driving your own car that can be used to get around town.

Maybe you should ask yourself these questions: Why are you driving anyways?  Is it really necessary?  If your answer is no, then can you drive during another time of day?  Can you just stay at home?  Can you walk?  Is your destination close enough to ride your bike to?

Now riding a bike opens up a whole new can of worms regarding helmet safety and riding bike_commuter-1on the road next to cars (see my blog post “Don’t Share The Road”).  Once I had a day off, so I took a 10 mile round trip on my bike to Wal-Mart to pick up my son’s eye glasses.  Now I know I probably wasn’t that 1% of traffic that was off the road but I was one less car.  If, for example, 100 people decided they didn’t really have to be on the road and instead stayed home, walked, rode their bike or took public transport, would traffic congestion be less?  Maybe.

Now I’m not one of those tree-hugging, EPA loving, Global Warming, Al Gore sympathizers who think that most of the world’s major cities will be under water by the year 2020 if we keep “poisoning” the atmosphere by driving vehicles with combustion engines.  Now you know where I stand on those issues!  All I’m saying is that if you don’t have to drive during rush hour, there are other options out there.

Issue Number Four – The Unnecessary Traffic Jam

             Problem: “Rubber-Necking”

Preview (1)Sometimes interstate traffic jams up for no reason at all.  There’s no accident, there’s no police activity, there’s no tangible reason to hit the brakes — only to prevent from rear-ending the car in front of you.  Other times, there might be a traffic jam or emergency vehicles…in the opposite lane.

People are curious by nature and “rubber-necking” is caused whenever a driver sees an overturned vehicle, a brush fire, another traffic jam, a Sasquatch or emergency lights.  “Rubber-necking” is the behavior of gaping or focusing on something of significance.  A frequent example of this is drivers attempting to regard the outcome of a motor vehicle accident.  The concept of “rubber-necking” relates to the physical act of stretching one’s neck, achieved in order to get a better view (Partridge, et. al, 1994).

Rubber-necking (or as it will now be referred to as “idiot-gazing”) has been labeled as a human characteristic that is related to brooding interest or desire (Franklin, Daniel, 2006).  “Idiot-gazing” can be a major contributor to of traffic jams (sometimes known as “Gapers’ blocks”), as drivers slow down to gaze at a vehicle accident.  “Idiot-gazing” may also cause additional accidents in the lanes traveling the opposite direction of the original accident.  Many times, drivers become engrossed in the sight of an overturned vehicle or emergency lights and suddenly alter their rate of travel, while other drivers behind them are also distracted, and thus another accident occurs.

635873735760104112-1157519785_imageAn analysis on the English M6 motorway discovered that 29% of accidents and breakdowns resulted in slow-downs in the uninvolved opposite lanes (Doward, et. al, 2009).  An analysis in 2003 in the US found that “idiot-gazing” (“rubber-necking”) created 16% of distraction-related traffic accidents (Lee, 2004).

There was once a wild fire on C-470 on one of the hog-backs near Ken-Caryl Ave.  I merged onto the highway about 15 miles away from the emergency and could see a pillar of smoke rising to the sky.  As I got closer, about 5 miles away, I realized that traffic was slowing down.  I flipped on my radio and discovered what was going on.  Thankfully, my destination was a little before the fire and I exited off the highway without hitting much traffic.  Later that day, I drove on the stretch of highway that went right by the fire (that had been extinguished by then – thanks West Metro Fire!).  The fire was nowhere near the highway, yet both sides of the interstate were backed up.

I’m sure that every driver has experienced the frustration with “idiot-gazing”.  All it takes is one (or a few) drivers to look away from what they should be doing – driving – to what they shouldn’t be doing – looking away from the road at the traffic accident – and as a result, traffic behind them slows down.  There’s nothing that bothers me more than to get to the end of the traffic jam, just to realize that the only reason why it took me 20 minutes to go one mile is because there was an accident on the other side of the highway!

            Solution Number I: Keep Driving!keep-calm-and-keep-driving-10

“Rubber-necking” appears in the book “100 Most Dangerous Things in Everyday Life and What You Can Do About Them” by Laura Lee.  Here is what Lee recommends as the most harmless course of action to take when a driver sees flashing emergency lights and an accident: KEEP MOVING! – There is nothing to see here!  The influence and burden of “idiot-gazing” on vehicle traffic has been the theme of many studies (Teng, Masinick, 2004) and might even be integrated into highway design (Lee, 2004).

            Solution Number II: Incident Screens

The next solution to “idiot-gazing” is the brilliant creation of incident screens.  Whenever an accident occurs, an incident screen is placed around the scene so passing motorists can’t see what’s going on (Department of Transportation, 2008).  Incident screens are basically made up of chain-link fence sections with plastic inserts so drivers can’t see what’s on the other side.  The idea is to hinder “idiot-gazing” and promote the flow of traffic (BBC News, 2012).

The first to try this innovative technique was England.  In 2013, the British government incidentscreensdistributed 105 sets of incident screens to their Highway Agency.  They see it as a “great advantage”.  Each set has 30 screens, are carried by special trailers and can span up to 75 meters (246 feet) from one end to the other and are about 2 meters tall (6 ½ feet).   The total cost of the screens was £2.3 million (under $3.5 million US dollars), with each set costing £22,000 ($31,016 US dollars).  The British government estimates that incident screens will save their economy “tens of millions of pounds” every year (BBC News, 2012).

British roads minister Stephen Hammond said, “This will be another great advantage to hopefully clearing up collisions but also getting the roads moving rather more quickly afterwards.

“People will recognize these screens, recognize that something’s happening behind it, but actually realize it won’t impact on their motorway – there’s nothing to see, and we want to keep the motorways flowing.”

RAC Foundation director, Stephen Glaister, said the use of the screens should be welcomed, “Incident screens reduce disruption to traffic following an incident [and] assist the emergency services,” he said.

“Ensuring that motorists not involved in an incident complete their journeys safely and on time is important.

“The economy relies on an efficient road network.  Traffic jams following incidents increase frustration and the risk of low speed collisions.” (BBC News, 2012)

I have several hesitations to the use of these incident screens.  First of all, the cost.  While England is a rather small country, the United States is not.  Think of the enormous cost it will take to supply these screens to each state’s department of transportation.  Where will this expense come from?  Higher taxes?  Secondly, will these incident screens deter “idiot-gazing”?  Will the very existence of them on the other side of the road still cause drivers to slow down and gawk at them?  I wonder if there have been any studies on the results of incident screens.  Have they really increased traffic flow in an accident area?

The Final Solution: Robot Cars

We humans don’t possess the ability to keep an unchangeable, steady speed when we regard other motorists on the roads.  Our constant attention to the unpredictability of other drivers keeps our nerves on edge and contributes to variable speeds that can lead to traffic congestion.  During a study, Japanese scientists had people drive at the same speed around a circle.  Congestion emerged out of nowhere.  Drivers carelessly put on their brakes and began behaving distrustfully to drivers in front of them (Plumer, 2013).

A concept of a driverless car

Robot cars can do a lot to lessen traffic jams.  Imagine a day when every car on the road drives itself.  The passengers can leisurely sit back while their vehicle does all the work.  They don’t have to worry about speeding up to make a green light or when they need to merge onto another lane.  The passengers can simply sit back and read or go about their business.  The robot cars will communicate with each other so they know when another car is going to change lanes or slow down for a traffic light.  This would be great right?  Really, I don’t see this ever happening.  There’s something about having the power to operate my own vehicle.  It gives me freedom and independence.  Maybe there may someday be a special lane where robot cars drive.

The Google driverless car

Business Insider predicts that there will be 10 million self-driving cars on the roads by 2020.  Car manufacturers like Mercedes, BMW and Tesla have already made or will be making self-driving characteristics that give the car some ability to drive itself (Greenough, 2015).

Some technology companies are laying the groundwork for a 100% self-driving car.  Last year, Google tested its first driverless car model in California.  So the future doesn’t seem that far away!

In Conclusion…

Despite the efforts by many well meaning people and governments, I don’t think we will ever see the end of traffic jams.  As I stated before, there are many different types of people on the roads.  Some throw caution into the wind and can care less about other drivers, others drive safe but don’t impede on traffic flow and others drive so slowly that they really need to go back to driving school.

Unless you can grow wings and fly over the traffic jam or teleport yourself to your destination (wouldn’t that be cool?!), you will have to sit and wait.  It is one of the most frustrating, irritating things when you are late for something or just simply want to drive on a highway without these unfeeling, unsympathetic, uncaring drivers who keep putting on their brakes!

downloadI am one of the worst drivers when I approach a line of traffic that is at a stand-still.  I feel like shouting out of my window at whoever started this thing!  My knuckles turn white as I grip the steering wheel tighter!  I check my speedometer or my clock.  However, those techniques usually don’t solve anything!

The best thing to do is to pass your time doing things that will take your mind off the frustrating situation.  Talk to the passengers in the car with you, turn on some good music or listen to talk radio.  Talk to yourself about something…just don’t answer yourself!  Think about something else that will take you to another place and you will realize that the traffic jam isn’t so bad!  This doesn’t apply of course if the person sitting in the car with you is in labor.  In that case, drive as fast as you can on the shoulder with your hazards on and yell out your window when appropriate.  And remember…if everybody drove like me, there would be no traffic jams!


  1. What is a zipper merge? (2016). Minnesota Department of Transportation. Retrieved January 19, /2016, from
  1. Plumer, B. (2013, September 24). The weird, counter-intuitive science of traffic jams. Retrieved January 19, 2016, from
  1. University of Exeter. (2007, December 19). Traffic Jam Mystery Solved By Mathematicians. ScienceDaily. Retrieved January 19, 2016 from releases/ 2007/12/ 071219103102.htm
  1. Palca, J. (2013, November 29). Phantom Traffic Jams: What Causes Mysterious Highway Backups? Retrieved January 19, 2016, from
  1. Partridge, Eric; Beale, Paul (1994). Fergusson, Rosalind, ed. Shorter Slang Dictionary. London: Routledge. p. 178. ISBN 978-0-415-08866-4.
  1. Franklin, Daniel P. (2006). Politics and Film: The Political Culture of Film in the United States. Rowman & Littlefield Publishers. p. 96. ISBN 978-0-7425-3808-5.
  1. Doward, Jamie; Slater, Chris (1 August 2009). “Giant screens at crash sites to end rubbernecking’ danger”. The Observer.
  1. Lee, Laura (July 1, 2004). 100 Most Dangerous Things in Everyday Life and What You Can Do About Them. Murdoch Books. p. 161. ISBN 978-1-74045-422-3.
  1. Teng, H; Masinick, Jonathan P (2004), An Analysis on the Impact of Rubbernecking on Urban Freeway Traffic, Report No. UVACTS-15-0-62, Center for Transportation Studies, University of Virginia
  1. “Incident Screens – Functional Specification”. Highways Agency. Department for Transport. August 2008. Retrieved 2013-08-26.
  1. “Motorway screens bid to stop rubbernecking by motorists”. BBC News. 27 December 2012. Retrieved 21 August 2014.
  1. Motorway screens bid to stop rubbernecking by motorists. (2012, December 27). Retrieved January 19, 2016, from

13.  Greenough, J. (2015, July 29). 10 million self-driving cars will be on the road by 2020.             Retrieved January 19, 2016, from million-           self-driving-cars-will-be-on-the-road-by-2020-2015-5-6


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