
Why a Traffic Flow Suddenly Turns into a Traffic Jam (2013) - dnetesn
http://nautil.us/issue/71/flow/why-a-traffic-flow-suddenly-turns-into-a-traffic-jam
======
fosk
In the US one of the biggest problems I have experienced is that drivers do
not adhere to the international rule of having slow drivers on the right side
of the freeway, especially in California.

As a result to this there are more lane splitting episodes (even within the
speed limit) in order to finally being able to keep moving at a faster speed
because the lane is effectively blocked by other drivers.

In addition to that, occasionally drivers will go faster (emergency, being
late, and so on) and those same slow drivers that occupy each one of the 5
lanes at the same time will amplify the lane splitting, ultimately causing
temporary traffic jams.

I never really understood why is this - in Europe we automatically merge to
the right and always try to keep the leftest lane available for whoever needs
to use it.

~~~
c22
One of the biggest problems I experience on freeways in the US is that
traveling 5 or even 10 mph above the posted speed limit makes you a "slow
driver". So even though you might feel that travelling at or above the
_maximum legal speed limit_ should give you the right to occupy the "fast"
lane someone will prove you wrong by screaming up your ass at 80 mph, 90 mph,
or more, flashing their high beams and becoming irate.

~~~
cryptonector
You don't get the "right" to "occupy" the left lane just because you're going
fast. You have the _obligation_ to _yield_ the passing lane to anyone who
wants to go faster.

You do not know who has an _emergency_ , and who doesn't. You don't get to
enforce one law (speed limits) and flout the other (yield the passing lane).
In fact, you don't get to enforce any laws if that isn't your job, and if it
were your job, you should not disregard one of those laws.

~~~
Scea91
What is the rule exactly?

1) Yield the passing lane for anyone that wants to go faster

or

2) Yield the passing lane if lane on the right is free.

I am asking because I am not sure, but (2) would make more sense to me. You
should not be required to break the speed limit to be allowed to pass the
slower traffic.

~~~
c22
It seems to vary by state (see the link I posted in a sibling of your comment)
but the general rule is that the left lane should _only_ be used for passing
in which case logically there should only be one "pass" happening at a time so
yielding is not an issue.

~~~
cryptonector
Of course, in heavy traffic this goes out the window.

------
eljefe900
This article doesn’t mention a strategy you can take for breaking the wave:

[http://trafficwaves.org/](http://trafficwaves.org/)

I originally found this info via the happy mutants at boingboing:

[https://boingboing.net/2013/06/23/howto-singlehandedly-
erase...](https://boingboing.net/2013/06/23/howto-singlehandedly-erase-
tra.html)

After using this technique for years, I can tell you that changing your mode
of driving when you encounter traffic is difficult. Especially when you’re not
used to “letting people pass”. But I’m convinced it helps break the jams.

I wonder if the autonomous vehicles in our future could adopt a similar
strategy when encountering traffic to reduce jams for all of us even if
they’re a small percentage of the overall drivers.

~~~
40four
I liked the article, but I agree they should have made the way to correct this
more clear. They briefly mention to increase you 'headway' in the end. I wish
they would have hammered this point home, instead of waxing poetically about
fluid-dynamical models, & detonation waves.

The articles you linked do a great job at explaining how to fix this. Thanks
for that! I believe this information should be taught as a basic part of
drivers education.

I intuitively started doing this many years ago. To me, it was obvious. You
can see the wave of break lights in the distance, and the wave is slowly
moving back towards you. People are so impatient, they insist on riding the
bumper of the car in front of them, even in a traffic jam. Then they are
caught in the cycle of accelerating quickly, then coming to a full stop.

It's a simple fix. Drive slowly and steadily. Keep a large number of car
lengths between the car in front of you. If you can manage to maintain the gap
in front by the time you come to the back of the next 'jamiton', without
breaking or stopping, the Congratulations! You just 'erased' that jam, or the
wave of cars coming to a stop in that part of the jam.

All of the cars behind you will benefit. And if enough drivers were practicing
this, jams would be less & clear up faster.

You are right though, the hard part is learning to not care when impatient
drivers angrily speed around you, only to run up to the back of the (clearly
visible) stopped cars. I just smile and laugh at how silly they are, pat
myself on the back for being a smart driver, and a good citizen to all the
cars behind me ;)

~~~
mattrp
My view of jams is they are caused by three expectations drivers have: 1) that
the speed limit is still the “minimum speed” recommendation in heavy traffic.
Ie, if it’s 65, one can still attempt to drive 74. 2) that the left lane is
going to be the fastest in heavy traffic and 3) that somehow using the soon-
to-be-closed lane in a lane closure/traffic shift scenario is “skipping the
line.” In my view if we had adaptable speed limits /expectations of speed, we
could probably avoid jams altogether if everyone agreed that 35mph was an
optimal speed for heavy traffic. There would be far fewer brake lights and
people would have far better reaction times (provided the slower speed didn’t
give them false sense of security leading to checking their cell phones). In
any case, try this the next time you’re in a jam- move to the right most lane.
Not only is everyone around you doing the opposite (trying to go left for
fast), but there are also people exiting the highway altogether... creating a
slightly faster moving lane.

------
legohead
I've been intrigued by traffic after moving to SoCal from Oklahoma. day after
day you will hit pockets of slowness only to find out there was no
obstruction.

in the past I read about 'shockwaves' in traffic. one guy changes lanes too
fast, which causes multiple lanes to hit their brakes, and then you get the
shockwave effect ("Jamiton" in this article) and it lasts a long time. but
after doing enough highway driving, I don't think that's the main issue.

my hypothesis is it's simply merging traffic. I've noticed on my daily routes
that traffic is always bad where there are a bunch of roads merging, and
immediately after all the merges finish, traffic speeds way up. bad drivers
aren't causing these shockwaves, it's all the sudden merging. I attribute this
to bad planning. "hey, this is a major road and it's going across the highway,
it should probably have a merge here."

a lot of people bring up zipper merging - better training of drivers will help
a bit, but properly planned highway merging would be much more efficient.

~~~
robmaister
I've found that a lot of times it's not an onramp merging into you, it's
people waiting until the last second to merge to an offramp and slamming on
the brakes and/or cutting off someone to not miss the exit.

I deal with this every day when I come home from work on my exit off the 405.
People don't want to wait in line because it's slow, but it's slow because
those people cut in at the last second and cause the entire lane to apply the
brakes.

The 405/55 interchange is another example of that, particularly 405N to 55N in
the evenings.

~~~
ikeyany
You are absolutely correct. In my experience, traffic is caused by drivers who
1) refuse to plan ahead and 2) are fine with fucking over other people in an
effort to mitigate that lack of planning ahead.

~~~
drewg123
You're being generous by saying they "refuse to plan ahead". I think they are
actively planning to "cheat" and cut in line, thus screwing over all traffic
behind them.

I deal with a merge every day where 3 interstates come together. The first two
(I64E, I195N) run together for 1/2 mile and finally merge from 2 lanes to one
_just before_ they merge into a dedicated lane on the destination interstate
(I95N). They recently (last year or so) added the dedicated merge lane on I95N
to try to speed things up, but it has not helped. The real problem is people
waiting until the last second to merge 2:1 for the merge on to the destination
highway.

I think things would be more effective if traffic from both interstates were
forced to merge to a single lane as early as possible. Then traffic would be
moving at close to the speed of the destination highway, rather than at 5mph
due to all the lane jockeying resulting from the 2:1 merge just before the
final merge onto I95N.

------
leoedin
There's been a big investment in the UK recently in "smart motorways"

[http://www.itsinternational.com/categories/detection-
monitor...](http://www.itsinternational.com/categories/detection-monitoring-
machine-vision/features/uk-defaults-to-hard-shoulder-running-to-expand-
motorway-capacity/)

[https://www.rac.co.uk/drive/advice/driving-advice/smart-
moto...](https://www.rac.co.uk/drive/advice/driving-advice/smart-motorways/)

These have overhead screens which show the speed limit (it's variable) and
whether each lane can be used. They also have a lot of speed cameras enforcing
that the displayed speed limit is being followed.

The intention is to keep traffic flowing at a much more consistent speed to
avoid bunching. It also means if something happens traffic can be slowed down
many miles away.

It essentially means the same road can have 30% greater capacity.

