

In-Car Algorithm Could Rapidly Dissolve Traffic Jams - munin
http://www.technologyreview.com/blog/arxiv/27166/?ref=rss

======
nlh
My hunch is that ultimately, ceding control of the car to an automated system
is going to produce better results, at least when driving on major "pipeline"
roads. The biggest source of traffic jams isn't necessarily the pure density
of cars, but the inefficiency of the individual driver. If each person takes
that extra second to accelerate, that gums up the whole works (in NYC we are
trained to be more efficient - taxis will honk at us if we take more than .05
seconds ;)

Imagine this: You enter a major arterial roadway -- I-95 or Route 80 and you
program your destination -- an exit #, a rest area, etc. Your car joins the
pipeline, syncs up with all the other cars on the road, accelerates to a
(fast) cruising speed (100+ mph), and you sit back and enjoy the ride. No
lane-changing, no "human" failures (like slowing down just because the sun
changes direction) - and when it comes time to arrive at your waypoint, the
system safely gets you out of the flow and into a "manual" lane. Then you take
over from there.

Could be awesome...

~~~
bdhe
Interestingly, this seems to converge towards traditional ways of mass
transit, like trains. Except for two crucial differences with regards to the
US: Insane connectivity, seeing how good the highway system is in the US, and
of course the fact that once you get off the freeway, you still have a car to
navigate through the vast suburbia (even if you have to do it manually). I
wonder if this will be the replacement for good mass transit in the US, at
least for now.

~~~
onemoreact
I think the final piece of this puzzle is going to have electrified highways
so you can travel long distances without the need for large battery packs. It
would still be more efficient to uses busses/trains but we already have a lot
of roads and cars which make retrofitting seem like the best option.

~~~
liotier
Yes - and we could replace the rubber/tarmac interface with a steel/steel one
for even better efficiency.

Highly automated steel-wheeled vehicle on steel tracks with continuous
electricity supply along the way... I wonder how we'll call that.

~~~
ebiester
So long as I don't have to walk a mile to get to the steel/steel in the
110+(F) sun, I don't care what you call it. ;)

------
ora600
Years ago I've read an article that recommended doing this manually as a way
to assist the flow of traffic.

I thought its a nice idea and tried it. Unfortunately, I tried this in Tel-
Aviv, where drivers from other lanes immediately moved their cars into the
space that opened between my car and the one ahead of me. It didn't take me
long to figure out that I'm getting nowhere.

Two years later, when I moved to the bay area, I tried it on the 101 during
rush hour traffic. To my shock, it worked. It was exceedingly rare to have any
car move into that space. Or move lanes in general. For some reason (laziness?
safety?), California drivers don't switch lanes as much as Israeli drivers do.

Moral: There's time and place for every algorithm.

~~~
blahedo
I've used a variant of this successfully when there's a merge coming up.
Basically, if I'm in the lane that's disappearing, I slow down as if to merge,
matching speed with the car next to me, but then _don't merge_ until the last
moment. When I do this I invariably get some hotshot honking behind me who
wants to zip up to the merge point and slow down traffic there, but such
people are essentially the cause of the problem, so I don't worry too much.

What generally happens is that from the moment I start doing this, overall
traffic speeds up just a bit and the lane ahead of me clears fairly quickly.
It's win-win for everyone but the hotshot behind me.

~~~
jawns
Actually, this is suboptimal.

The optimal flow is for everyone to use both lanes up until the last moment,
and then to merge by alternation (one car from one lane goes, then one car
from the other lane goes).

Unfortunately, this only works when a substantial majority of the drivers
understand that this is how it should work. If you don't hit that threshold,
then the people who use the disappearing lane are going to get glares.

Here's a link that describes the theory behind optimal merge patterns:

[http://jksqr.blogspot.com/2008/09/optimal-lane-merging-
part-...](http://jksqr.blogspot.com/2008/09/optimal-lane-merging-part-1.html)

~~~
wbeaty
Actually he may be forcing the lanes-full optimal mode to arise.

If one or a few drivers in the empty lane start pacing the cars in the full
lane, cars will build up behind them. When they arrive at the end of their
lane, the drivers in the full lane won't be so ready to block merges (since
nobody was cheating by racing down to the end.) Perhaps this could trigger an
outbreak of zipper-merging.

------
AretNCarlsen
I'll bet that you're thinking that this will have to wait a decade or two,
until every car on the road has a new generation of computers installed. Look
up a Mercedes product called Distronics Plus and a company called Autoliv.
These guys are already mounting stereo cameras and long-wavelength IR (heat)
cameras on _production_ luxury cars to detect turn signals, pedestrians, and
license plates of other cars. When 50% of cars have radars linked to their
cruise control, it's a matter of iteration to let them share data, then to
characterize the remaining vehicles on the road based on the aggregate
observational data.

Your '95 Civic may not be announcing its velocity, but when the car behind you
and the car in front of you have both read your license plate and agree on
your speed, you may as well be.

~~~
wbeaty
Prizewinning 2004 research by LC Davis of Umich showed that stop/go traffic
jams were eliminated by adding in a certain percentage of cars with Adaptive
Cruise Control (ACC.) It only took a little less than 1 in 5 cars.

<http://www.ur.umich.edu/0304/July19_04/19.shtml>

[http://www.google.com/search?q=%2Btraffic+jams+%2Bdavis+%2Ba...](http://www.google.com/search?q=%2Btraffic+jams+%2Bdavis+%2Bacc+%2B2004)

What does ACC do? It imposes proper safe driving headway distance, as well as
providing near-instant reaction time for braking. No tailgating, no
accumulation of 1-sec human reaction times.

But couldn't human drivers do the same by simply padding out their 2-sec
spacing to 3-sec? And only a few need to do it.

------
WalterBright
Huh, I've been using an "algorithm" for 30 years. I noticed on the freeway
that when traffic slows in front, drivers overreact and brake more than
necessary. This causes the driver behind to also brake more than necessary,
eventually slowing traffic to a complete stop.

The point where traffic stops then flows backwards along the freeway like a
wave. You can see this if you have a long view of the freeway ahead.

So what I'd do is slow down in advance of the wave reaching me, and try to
time it so that the traffic starts moving again before I reach the stoppage.
Many times, I've been able to stop the wave from progressing by doing this.

~~~
wbeaty
Rather than 100 automated cars, just use one daily commuter.

If you commute along a stretch of highway every day, then you know exactly
where the "stop waves" tend to appear. That's the place where you stop driving
like a Wolf, and instead drive like a Shepherd: stop speeding and tailgating,
and instead open up a large buffer.

I've found that this works well in some places. The other drivers seem to know
what you're doing, and sometimes you'll even see others using the same
technique. But in other spots everyone seems clueless, and they'll race to
fill up the tiniest hole.

Also, as with the Koshima monkeys washing potatos or Blue Tits & milk bottles,
in the last ten years the trick seems to be spreading. Some of our "clueless"
regions have experienced a state change, and the daily jams seem to appear
less often.

I wonder if the articles below have a simple cause:

[http://blog.tstc.org/2010/09/23/u-s-traffic-fatalities-
plumm...](http://blog.tstc.org/2010/09/23/u-s-traffic-fatalities-plummet-but-
why/)

[http://cityroom.blogs.nytimes.com/2010/01/27/2009-traffic-
de...](http://cityroom.blogs.nytimes.com/2010/01/27/2009-traffic-deaths-were-
the-lowest-in-a-century/)

[http://www.usatoday.com/news/nation/2010-09-09-1Aroaddeaths0...](http://www.usatoday.com/news/nation/2010-09-09-1Aroaddeaths09_ST_N.htm)

------
bmohlenhoff
Neat idea, I like the idea of a somewhat intelligent "traffic swarm", but the
article doesn't address what effects a malicious player could induce on the
scheme. What's to stop people from randomly broadcasting "Traffic Jam Ahead"
signals to cause slowdowns, or maybe even "Traffic Jam Behind" to cause the
vehicles to suddenly accelerate? Considering that, I think it would be
possible to come up with an aftermarket module to regulate the behavior of the
traffic swarm such that the user would reach his destination faster at the
expense of slowing the rest of the swarm down. Any traffic swarming scheme
needs to take this type of behavior into account, or else I don't think it
would work out very well in practice.

~~~
jjmaxwell4
I thought the article was just saying that the cars will broadcast their
speed. In this way cars will know if they are slowing down ahead of them, and
it will be built in, so it won't be easily hackable like you described.

Things like this could possibly save Millons of hours a year. Quite powerful.

~~~
djb_hackernews
If it can be hacked, it will be hacked. Just because it's built in means
nothing. In fact, I bet it makes it a bigger target.

~~~
jjmaxwell4
Ya I know. I meant hacked as in regular drivers randomly broadcasting signals
saying traffic jam ahead. Obviously it can be hacked, but it will have to be a
lot more sophisticated then that.

------
jawns
Sounds like this technique can be imperfectly implemented without any new
technology.

Just encourage people to use defensive behavior when they see a jam up ahead,
and optimistic behavior as they leave the jam.

Sure, that's limited to people's line of sight (in the case of approaching the
jam), but it's better than nothing.

Interestingly, I've been assuming both optimal behaviors intuitively. When I
see a jam up ahead, I slow down well ahead of time, hoping that by slowing
now, I'll avoid a full stop up ahead; similarly, as soon as I get out of the
jam, I speed up quickly. Seems like the natural thing to do after a traffic
delay.

~~~
rix0r
We have that system already (at least, here in the Netherlands), where
automated overhead signs urge you to decrease your speed in case of traffic
jams.

In my experience, not a single person follows those signs. Everybody just
keeps on going at full speed until they're forced to stop.

It would be a lot better (for everyone!) if cars were driven by machines that
followed those rules properly.

~~~
Symmetry
Yup. Game theory exists for a reason, people doing public policy should think
about its predictions.

~~~
CWuestefeld
People doing public policy _not_ thinking about its predictions, is one of its
predictions.

------
username3
SCIENCE HOBBYIST: Traffic Waves, physics for bored commuters
<http://trafficwaves.org/>

~~~
lutorm
I always try to do the "average speed" thing in stop and go traffic (if for no
other reason that I have a manual transmission and it's really annoying to
have to stop and start...) and it has another effect that this page did not
mention. The spaces that open up in front of you can often be quite large, and
a substantial fraction of the drivers behind you (who presumably have not
learned about travelling waves) will honk, flash their light, or even cut into
the other lane, pass, cut back in front of you, speed up to 60mph and then
slam to a stop, just because you are obviously "not keeping up with traffic".

------
pkamb
I-5 into Seattle has networked variable Speed Limit signs that reduce the
speed for people approaching traffic jams. Same idea as this article I think,
but no need for transceivers in every car.

------
wisty
It won't work while you have aggressive drivers messing with the system.

There's a legal solution - create cameras that detect tailgaters, and fine
them. That will encourage people to leave more space, which will give everyone
more room to maneuver. Country-town car spacing = country town speeds, not the
~10mph you get in city centers.

~~~
john_b
I think a technical solution for a technical problem is better than a legal
solution to a technical problem, especially since the hardware and
infrastructure for such a widespread camera system (not to mention the
associated state bureaucracy that would be required to operate it and process
the fines) would be unavoidably expensive. Even if it were somehow cheap and
simple, monitoring every piece of road would be impossible. And then you would
need to legally define "tailgating" and correct for edge cases such as when
the person in front brakes suddenly, but the camera still sees it as
tailgating.

------
cjauvin
Interesting idea, although the part where the car starts to "accelerate away
quickly using automated cruise control", to leave the jam, sounds a bit
scary..

~~~
singer
Ford Explorers (and possibly other) have adaptive (automated) cruise control.
It's not really scary at all because it measures the distance between your car
and the car in front of you, and determines the proper speed to drive. It's no
different than you performing that calculation in your head and making the
correct adjustment to the gas peddle.

~~~
weaksauce
Still a bit scary... Did you see the Volvo demo video of the exact same
technology you describe go full speed into the back of a truck?

~~~
AretNCarlsen
Yes, and "if Captain Sully had been flying an Airbus he would have crashed
because they don't allow manual control". The objective is to reduce the total
number of crashes, even if that means that you feel like you have less control
of when you do crash.

------
joelthelion
If you want to play with a simple traffic flow cellular automaton, check out
this quick C++ gist: <https://gist.github.com/1199391>

More discussion at reddit:
[http://www.reddit.com/r/math/comments/k6ked/can_you_guess_wh...](http://www.reddit.com/r/math/comments/k6ked/can_you_guess_what_this_sequence_is/)

------
eggoa
Here's my algorithm: everyone drives "defensive" all the time.

No new computers needed, and fewer "optimists" rear ending people.

~~~
AndyJPartridge
I like that idea, and I'd add it to mine:

People drive at a constant speed.

The root cause of traffic jams, in my opinion, is that people brake much
quicker than they accelerate.

This leads to traffic bunching up, and then stretching out as people regain
speed.

In the UK, the variable speed limits on major routes work if people obey them,
as it cuts down this emergent behaviour.

------
lcargill99
You can do this yourself. Just leave space. Others will see you do this and
leave space, too. While making this a science project sounds like fun, that
seems unnecessary.

If the traffic pattern is so saturated that people rush into the space you
leave, leave space _anyway_. Leave more space.

People seem to want to optimize for "average distance from the destination".
That doesn't get them there any quicker.

~~~
icebraining
_> Others will see you do this and leave space, too._

You certainly don't drive where I live.

------
lutorm
I think the really cool potential for traffic jam abatement is when basically
everyone uses on-line GPS routing (like Google maps), which can dynamically
route vehicles based on the traffic density to approach a global minimum.

There is actually research about this, like
<http://papers.ssrn.com/sol3/papers.cfm?abstract_id=577201>

------
slmbrhrt
Reminds me of this:

[http://www.cs.utexas.edu/~pstone/Papers/bib2html/b2hd-
trr11....](http://www.cs.utexas.edu/~pstone/Papers/bib2html/b2hd-trr11.html)

Looks like he's redesigned his homepage since I got my degree, so I can't
immediately find the animations he used to have to illustrate the method.

------
rmc
_It also requires a little more automated on-board control than cars currently
have but not an unrealistic amount._

That's going to be the biggest problem. Automatic driving of cars isn't a
technical problem where you need to tweak something, it's a legal problem.

------
vladoh
This solution will never work. Almost all cars should be equipped with the
system, which is very difficult task. And just look at this sentence: "At the
same time, vehicles leaving the jams are made to accelerate away quickly using
automated cruise control." The car accelerating by itself... this is madness.

A lot better way to dissolve would be to show the drivers the traffic jam on
the map so they take another way that is free. This is the main idea of this
system:

[http://www.bmw.com/com/en/insights/technology/connecteddrive...](http://www.bmw.com/com/en/insights/technology/connecteddrive/2010/convenience/travel_navigation/bmw_rtti.html)

I have used it and it really works, because you can see the traffic jam in
advance and plan another route (or the navi can do it for you).

------
xutopia
What happens if driving becomes painless. Won't you have more drivers on the
road?

~~~
sp332
Quite possibly. Someone noticed that the actual speed of traffic in London is
always 9 miles per hour. If traffic improves, more people drive until it gets
down to 9 mph. If traffic gets worse, people decide driving is too much
trouble and traffic improves to 9 mph :)

------
chopsueyar
[http://www.smartmotorist.com/traffic-and-safety-
guideline/ma...](http://www.smartmotorist.com/traffic-and-safety-
guideline/maintain-a-safe-following-distance-the-3-second-rule.html)

------
83457
Automated cars = less traffic jams. That was easy.

------
ww520
Installing speed rely in every car might be unpractical and expensive. How
about install road sensors and displays flow speed on the side of the road?

Currently people use brake light to signal and detect slowdown ahead, but
sometimes people slow down without hitting the brakes. Displaying flow speed
every 500 or 1000 feet on the side of the road would give fore warning on
traffic slowdown ahead.

------
basseq
"That's an interesting and simple approach that could be implemented
relatively easily in the next generation of cars."

Yep, just as soon as we have cars that can not only drive themselves, but we
trust enough to cede control. Next generation? I doubt it.

~~~
zaphar
Google has cars that drive themselves in stop and go traffic with pedestrians
present already. Next Generation? Closer than you think.

------
Apocryphon
Why do I get the impression that trying to stop traffic jams is about as
futile as trying to predict the stock market?

