Traffic throughput - we can all get along, but not you tailgaters!  Enjoy.

Thanks to Mr B and Boost for finding this.  (NSW RUH imparts the three
second rule, counted as one, two, three without the word 'thousand', works
out about the same as the two second rule when spoken wioth the 'thousand').

http://physicsbuzz.physicscentral.com/2009/07/jerks-actually-reduce-risk-of-traf
fic.html

The next time someone cuts you off on your morning commute, don't be so
quick to call the driver a jerk; you may have a reason to say thanks.
According to the latest physics research, rule-breakers-drivers passing you
on the wrong side or changing lanes too close to the intersection-actually
help smooth the flow of traffic for the rest of us.

"The interesting finding is that if most of the people are law-abiding, and
you have a certain amount of people who are breaking the rule, then you are
actually getting the minimum chance of a [traffic] jam," said Petter
Minnhagen, a physicist at Sweden's Umea University and an author of the
paper published in the journal Physical Review E.

Physicists at the school uncovered this phenomenon while constructing a
computer model of how a crowd of people move across a confined space, such
as a pedestrian-only street. They divided the space into squares, like a
chessboard, and randomly placed pedestrians in some of the squares. Like
real people, the model pedestrians had a certain small probability of
momentarily pausing, as if they had run into a friend or had bent down to
tie a shoelace.

To make things more interesting, the researchers then tossed a few mavericks
into the mix, who didn't follow the rules the other pedestrians used. The
physicists ran the simulation over and over, each time boosting the
percentage of rule-breakers. At first pedestrian deadlocks worsened. But as
more and more rule-breakers joined the fray, something entirely unexpected
occurred: traffic flowed best when only about 60 percent of pedestrians were
obeying the rules.

Simple interactions of individual cars, people, or molecules add up to large
patterns in a system. The high concentration of pedestrians in a small area
increases the chances of a jam, but rule-breakers made the crowds spread
out.

Morris Flynn, a University of Alberta professor who uses computational
methods to study car traffic, agrees with the explanation. Because
rule-breakers "carve out their own path," Flynn said, they dilute large
concentrations of rule-abiders moving in the same way. He pointed out an
example familiar to anyone who has driven on a two-lane road: breaking the
speed limit to pass a slow vehicle prevents a long chain of cars from
forming.

However, there is one rule you shouldn't break, according to a new analysis
of how high-volume traffic flows along a highway. Cecile Appert-Rolland, a
physicist at the University of Paris-Sud, looked at the tailing distances
between cars traveling on a busy two-lane expressway in the suburbs of
Paris. Most people have heard of the "three-second rule" for following
distances; after the car ahead of you passes a point on the road, count to
three. If you pass the same object before you get to three, you're following
too closely. This time-based measure of the distance between cars is what
Appert-Rolland terms the "time headway."

Her research showed that tailgating drivers were more likely than a
non-tailgater to have a car in the lane next to them, so they weren't just
speeding up in order to change lanes. She also found that these short time
headways tended to extend across several vehicles, creating a platoon.

"We can identify at least seven or eight cars where they have time headways
of half a second," she said. Considering that a driver's reaction time is
about one second, these platoons are disastrous pileups waiting to happen.
"If the first one brakes, the second one has to brake harder, the third one
even harder, and the last wouldn't be able to brake hard enough."

So while unexpected behavior may help with congestion, always follow the
three-second rule-because if you're tailgating, chances are you won't be the
only one.

R, J