
The weird, counter-intuitive science of traffic jams - Libertatea
http://www.washingtonpost.com/blogs/wonkblog/wp/2013/09/24/heres-how-self-driving-cars-could-clear-up-traffic-jams/?tid=rssfeed
======
twoodfin
_One study that tracked drivers in Boston during rush hour found that if you
could remove just 1 percent of people on the road (say, to mass transit), you
could achieve a whopping 18 percent improvement in traffic flow. But for
whatever reason, cities haven 't figured out how to do that just yet._

If you don't think in static terms, this is obvious. Across any segment of
time, some fraction of commuters will change their habits based on their
expectations of time/cost/comfort. Some commuters can respond daily if, for
example, they have a car and affordable parking at their destination as well
as access to public transit. Other commuters may not have a car at all but
will eventually buy one if it begins to offer substantial advantages over its
cost. The point is that the system is dynamic.

And if, magically, the City of Boston could wave a wand and redirect 1% of its
commuters to the subway, they'd soon discover that the 18% improvement in
traffic flow has tempted many other commuters back onto the roads, and the
benefit vanishes.

~~~
markbernard
People don't want to move to mass transit because it sucks. During rush hour
it only takes me 25 minutes to drive to work. If I took the bus it takes 2
hours. You will never get me to give up my car with times like that.

------
bryanlarsen
"people in convertibles are less likely to honk"

I think that there should be a law that a car's horn should be as loud inside
the car as it is outside. That's how loud it is for nearby cyclists &
pedestrians -- drivers would be much more likely to use their horn only when
it's really needed if it was as loud for them as it is for others.

~~~
ImprovedSilence
Meh, horns are a form of communication. Nobody honks a horn just for the hell
of it. Sometimes you just gotta make others aware of the situation.

~~~
bryanlarsen
Of course they have a reason to honk. I just want it to be a good reason. My
pet peeve is people who honk their horns rather than ring somebody's doorbell
because they're too lazy to get out of their car.

------
plg
A large component of driving around in cars, at least for many, many people in
north america, is not just for the purposes of transportation but
simultaneously for displaying an expression of your personality. Many people
buy particular cars because they view them as an expression of their
personality (or an expression of their aspirations). Sure, this may be the
"fault" of the car industry ... but whatever the origin, the fact is that it
is the case today.

What's more I think that the manner in which many people drive is also an
expression of their personality. Sure, some people buy a toyota tercel and
drive around in a machine-like state, purely for the purpose of transportation
... but I think the majority of people drive in a more "personalized" manner,
for lack of a better term.

I'm sure it's the case that google-self-driving-cars will be more efficient
(and safer) transportation devices ... but the challenge will be that the
masses will not easily migrate away from their personality-extensions
(mustang, bmw, cadillac, convertible, truck, etc) into a pod-like utilitarian
mode of transportation.

No doubt, one reason why traffic is so inefficient is precisely because of
these "personality" effects ... but there is much in life that is inefficient.
In an age of google (and others) identifying the "inefficiencies" in our daily
lives, we need to have a discussion about what features of our behaviour, and
our daily lives, define us as individuals and make us human.

Of course if part of your "personality" involves driving recklessly or putting
people in danger, this is not a good state of affairs. But you get the gist of
what I'm saying...

~~~
redwood
On the other hand, the same could be said about the phone... A major
personality device.

Imagine the 80s exec on his office phone behind the leather desk.

The power player in the early 90s in a "CAR phone".

The suburbanite with the really long cord so he/she can use the phone anywhere
in the living room/kitchen vicinity.

etc.

All of these were replaced by mobile phones which also become diversified as
personality brands. The same will no doubt happen with self driven cars.

So let's look for what the equivalent of the pickup, mustang, or prius will be
in the self-driven era.

My prediction: \- Mustang will be fast looking, but self-driven. With a manual
option (for driving on a track some place) \- Pickup will be strong looking,
but self-driven and with a manual mode expected to be used a lot \- Prius will
be small and utilitarian looking, without much expectation to be manually
driven

~~~
plg
interesting. I suppose even if it's a dialed-down version, a company could
easily provide self-driven cars that at least claimed to have different
personalities. Maybe that will be in the form of non-functional "flair"
(colours, decals, decorations, etc) but it has worked for many other products,
that's for sure.

cool

------
kps
The article is fairly unimaginative.

First, when most vehicles are self-driving, you no longer need traffic lights
or lanes. An urban street that is currently 2+2 lanes could be used as 4+1 in
the morning and 1+4 in the evening if that is what traffic requires.

Second, self-driving vehicles remove a current disincentive to commuter
microcars. A single person could easily get around in a car a third the size
of a current subcompact if they didn't have to worry about being run over by
land yachts. Beyond the lower cost, a half-lane vehicle could have a speed
advantage in urban traffic.

~~~
nkoren
Sure, if you have 100% self-driving vehicles with good vehicle-to-vehicle
communications, you can even do intersections like this:

[http://vimeo.com/37751380](http://vimeo.com/37751380)

However, there's one further requirement for removing traffic lights and lanes
and such: no pedestrians (try to imagine crossing the street in the above
simulation). If you believe that cities should be designed for human beings,
then this is a real problem.

So let's say you want to remove the traffic lights and create a high-speed
continuous-flow system comprised of lightweight energy-efficient micro-cars.
How could you make this compatible with human habitation? By removing the
roads entirely, and running the vehicles on cheap segregated infrastructure,
either below or above ground.

Sound fanciful? This technology already exists, and is much more mature than
self-driving cars. It's called "Personal Rapid Transit"
([http://en.wikipedia.org/wiki/Personal_rapid_transit](http://en.wikipedia.org/wiki/Personal_rapid_transit)),
and has been prototyped successfully for decades. The first commercial system
began operating in 2010, and there are now three PRT networks in public
operation (The Masdar Institute in Abu Dhabi, Terminal 5 at London Heathrow
Airport, and a national park in Suncheon South Korea).

When it comes to self-driving cars, freeways / motorways will be relatively
easy to automate, because they are already pedestrian-free continuous-flow
environments. I expect to see vehicles available which can do that by the end
of this decade, or possibly early next decade. Mixed-mode surface streets will
be far more difficult, however, and while they are likely to become automated
in the longer term, I suspect that this will only happen at very low speeds --
possibly as low as 10 km/hr, which is the speed at which humans and vehicles
can interoperate in a truly safe manner.

~~~
flatline
> try to imagine crossing the street in the above simulation

Just start walking, the cars will steer around you! More seriously, there are
already separate express and local routes for many major roads across the US,
I don't think it has to be a radical departure from what is already there.
Best part is, the way that self-driving cars are progressing to drive on
regular roads, the infrastructure can grow more specialized for self-driving
cars organically over time.

~~~
jerf
I will be intrigued to see the psychology of how that plays out, once people
are comfortable with self-driving cars. Are we going to appreciate being in an
intersection in which a care is approaching our side at 40 mph? Are people
going to just charge out into traffic and trust the cars to reroute, if that
turns out to be possible? (It may not be for various reasons, but let's run
with it.)

~~~
yaeger
Why would people have to run into traffic at all?

I'd say the easiest way to have streets with self driving cars and without
traffic lights would be to build pedestrian overpasses. Just a nice small
bridge to cross the roads.

------
Qantourisc
A lot of traffic jams are the result of an improperly tuned car-accelerations
and deceleration resulting in oscillations in the system.

Learn people how to drive properly and keep their distance and things will be
better. A good indication is on how much fuel you used in the traffic jam.
(Electric car excluded).

An auto-distance holder also helps to reduce the oscillation by 1 car, however
correctly adjusting by hand is better.

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

~~~
seanmcdirmid
I'm guessing this only applies to America. Where I'm from, traffic jams result
from ~150-200% over utilization rates. Accidents just make that worse.

~~~
Qantourisc
At my country it's also over-utilized, yet, you often see cars going slow, and
then you do stop, for no reason, that can't be good for the little throughput
you have left.

It won't fix it then, but it should help.

~~~
seanmcdirmid
When your entire commute is stop and go, I don't see much hope in merely
retraining the drivers. Self driving cars, on the other hand, can really
optimize how limited capacity is utilized in developing countries like china
(stuck in traffic right now in Beijing, which is way too normal here).

------
tmuir
Merging at the last possible moment _increases_ congestion. If there is a lane
elimination, after the the lane has been eliminated, traffic speeds up,
because there is no remaining merging to complete. Thus, the earlier merging
is completed, the sooner traffic can recover from the disruption. Also,
spreading out the merges over a longer distance, versus everyone merging in
the same spot allows traffic to recover from many small distributed
disruptions instead of one centralized large disruption. Early merging = less
traffic.

~~~
CanSpice
Do you have any proof for this, or is it just baseless conjecture? I suspect
the latter, because nearly every link when you search for "traffic merging
studies" states that late merging is more effective at reducing congestion.

From the Minnesota DOT: "Minnesota DOT engineers developed what they call a
"zipper," which meshes cars quickly. Signs advise drivers of the upcoming lane
closure, tell them to use both lanes up to a point and then direct them to
take turns merging. When traffic is flowing, drivers merge early to avoid
unsafe maneuvers. But when traffic is congested, motorists make full use of
both lanes. The data revealed that the change reduced traffic lines by 35
percent and also brought down "lane changing conflicts," says Craig
Mittelstadt, Minnesota DOT's work zone safety specialist."

From the Virginia DOT: "The late merge should be considered for 2-to-1 lane
closure configurations to improve throughput when large numbers of heavy
vehicles are present (>20 percent) for the majority of the time and congestion
and queuing are often present."

~~~
tmuir
"Do you have any proof for this, or is it just baseless conjecture?"

You mean, besides empirical evidence? Nope.

I see it almost every day on my commute, which is riddled with construction.
On the days that everyone merges well before the last possible moment, traffic
moves at a quicker pace, because there is no one to cut you off, and my
commute is shorter. On days that people decide to cut others off at the last
moment, my commute is measurably longer.

If you merge ahead of time, you are more likely to find an existing gap in
traffic, which has little to no effect on the traffic's speed. Whereas, if you
are merging at the last possible moment, you are necessitating a gap be
created specifically for you, forcing others to slow down.

If cars stay in the eliminated lane until the last moment, and then the speed
of traffic increases after the bottle neck, it was the merging at the last
possible moment that caused the slow down in the first place.

~~~
jedberg
And this is why traffic sucks -- because people prefer to rely on anecdote
instead of hard scientific facts.

The behavior you are observing is not zipper merging -- it's people being
assholes and trying to skip traffic.

If _everyone_ merged at the last second it would move better.

~~~
tmuir
From Wikipedia: "Anecdotal evidence is an informal account of evidence in the
form of an anecdote. The term is often used in contrast to scientific
evidence, as evidence that cannot be investigated using the scientific
method."

I didn't say "this one time back in 2001". This is everyday for years. These
are consistently observable data. Cars merge early, my commute is under 30
minutes. Cars merge late, and not just one or two (the north shore of chicago
is chock full of entitled assholes), my commute is over 40 minutes. Sounds
like a falsifiable hypothesis to me.

One of the main reasons airplanes and trains are much safer than automobiles
is that planes and trains have outside coordination of traffic, a third party
who can see the bigger picture. Automobile traffic is thousands of individual
actors who focus mainly on their own interests, and consider others around
them only to avoid near term problems. Hoping everyone will magically act in
concert, without government enforced obligation, is a pipe dream. Which is
what the article points to, and proposes to solve with self driving cars. Self
driving cars would allow the outside coordination that could facilitate zipper
merging.

~~~
jedberg
Your data is an anecdote because it isn't a repeatable environment with a
proper control.

~~~
tmuir
I'll have to try one that the next time I disagree with anyone about anything.
And to think, I've been relying on logic and reason this whole time!

------
JonSkeptic
My problem with self driving cars is not actually with self driving cars. I
trust that our technology can reliably enable a vehicle to drive me around
without my intervention. That's fine.

There are two things I do not trust: I do not trust that our technology can
successfully and intelligently respond in the event of an traffic or roadway
anomaly, the kind that usually causes car crashes i.e. damaged roads, debris
falling off of cars, erratic drivers, etc. Although I do trust safety
features, which are pretty nice lately, I would rather have not have a wreck.

Finally, I do not trust other drivers and I do not know how they will
react/interact with a self driving car. It only takes one time for an idiot to
flip out on the highway and cause a wreck.

When I feel that the self driving can adequately handle anomalies, wrecks, and
suicidally bad drivers, then I will have no qualms with the self driving car.
Till then, I'm not willing to bet my life that it works well enough.

~~~
bentcorner
What we need is a Robo-Indy 500. Companies with the latest tech in driverless
cars compete, and the public sees how well (or poorly) the technology can deal
with rapidly changing situations. Sure, you don't need to deal with peds or
other urban obstacles, but it would go a long way towards assuring the public
that driverless cars are safe.

~~~
SupremumLimit
Obstacles could also be incorporated into the race.

------
jaynos
Additionally, self driving cars would leave you free to read or surf the web
during your commute. If you're relaxing and not driving, who cares if the
commute takes a few more minutes...this would lead to a lot less lane
changing, tail-gating, cutting people off, and many other causes of accidents
and braking.

~~~
hrkristian
This is my main point when discussing self-driving cars. Every minute spent on
a commute is essentially time wasted, if I could do whatever I wanted while
driving I wouldn't mind an hour long commute.

The fact that we'd be distanced from the stress of driving, as you say, is
also a great benefit, we're not really made for coping with the irritating
nature of congested driving.

------
Shivetya
I think the real revolution will be in long haul trucking, self driving trucks
would go a long way towards increased delivery speed and safety. Throw in a
standardized communications protocol and they could be tapped by a variety of
services to relay real time traffic information, road conditions, and whatnot.
They could be tossed into HOV lanes if isolation in city limits is preferred.

As to the article, in Atlanta one major change that helped congestion was to
implement throttled access via on ramps governed by lights. This tends to keep
people from merging in groups which has a rubber band effect on existing
traffic.

Still more can be done by restricting areas of the highway to limit the lane
changes. In Chicago I saw this done with bypass areas separated by cement
walls. A simple solution but a bit cumbersome. Still separating some outside
lanes would help.

~~~
seanmcdirmid
Traffic on an entire urban freeway can be synchronized if automated, leading
to huge bandwidth increases. In America, you might say whatever, but in china
this will be transformative since there is nowhere else to build new
roads...and the authoritarian government can easily deal with those who still
want to drive themselves.

------
sambeau
The two main ways self-driving cars could clear up traffic jams are:

* Far fewer cars needed — as more cars could be shared

* Far fewer parked cars — as cars needn't stay with the 'driver'

The two cases are linked: a car that doesn't have to wait around where the
passengers are dropped off can return to base or can be away performing more
lifts while the original passengers are busy.

Families would have need for fewer vehicles. Sharing a vehicle would make more
sense.

If cars are busy during a drop-off-pick-up cycle there is no need for them to
be clogging up the streets.

~~~
dalore
Cue traffic jam of cars with no drivers because they are trying to get to
their next passenger/base.

~~~
sambeau
While there may be more cars doing return journeys I suspect there will not be
the same level of traffic jams as the cars return.

1\. Most outward trips would be chained: drop 1, drop 2, drop 3, return to
base; rather than: drop 1, return to base, drop 2, return to base, drop 3,
return to base. As would most return journeys.

2\. The roads would be clearer in cities due to fewer parked cars. In some
cases there would be an extra lane now available.

3\. Cars could still have multiple bases, especially if they are shared. Car
parks could be re-utilised as a stop-off points where empty cars could 'swap
out' and remove themselves from the system briefly.

4\. Chains could be linked: do the early run, do the late run. Do the Smiths;
do the Joneses.

5\. Empty cars with no urgent pick-up could wait for the roads to clear before
embarking on a return journey.

6\. Would anyone care if a car returns to base slowly if there wasn't an
urgent passenger waiting?

Cars could be more efficiently used and that would certainly imply that the
fewer number of cars in existence would be being used for more trips
throughout the day.

I admit that it will be hard to remove the rush-hour problem entirely without
a significant amount of car-sharing. However with a fully self-driving system
cars could do clever passenger shares (and/or mid-route swaps). Passengers
would be free to only car-share within their sex / family / workplace / social
networks etc.

------
jonnathanson
An interesting corollary: removing traffic lights in busy intersections might
reduce accidents and improve traffic flow.

Some small pilot studies have been carried out in Europe, often with
successful results. Basically, the idea is that we become more alert when a
situation requires us to be. An intersection that appears riskier forces us to
give it more conscious _and_ subconscious attention.

[http://knowledge.allianz.com/mobility/transportation_safety/...](http://knowledge.allianz.com/mobility/transportation_safety/?1841/risker-
streets-reduce-accidents)

Anecdotally, I can certainly testify to the effects of traffic lights on
traffic. I grew up and worked for a lot of my life in LA, a city as famous for
its traffic as for its movies and weather. There are certain parts of the city
in which every damned block has a traffic light, and blocks are very short in
the denser areas. These areas are traffic hellholes. Beverly Hills in rush
hour would have made a cameo appearance in Dante's _Inferno_ , had he been
around to experience it.

~~~
pak
Too many unsynched traffic lights in a grid formation often results in you
sitting at a red light with no traffic moving in front of you, which is
infuriating and inefficient. (Case in point, besides LA, is Toronto which
seems to be designed this way on purpose.) This situation is alleviated by
stop signs or traffic circles that give you the ability to advance when there
is, in fact, no cross traffic.

------
mathattack
_— Cars tend to drive closer to bicyclists who are wearing helmets. That comes
from Ian Walker, who set up a bicycle with sensors and drove around the city.
Vehicles tend to crowd closer to him when he was wearing a helmet than when he
wasn 't. That's not necessarily surprising, but it's a reminder of all the
weird unconscious tics we adopt while driving and making on-the-fly
assumptions._

This is a weird adaptation of the Peltzman effect[1], which found that people
drove more recklessly when wearing seatbelts.

[1] [http://gregmankiw.blogspot.com/2006/07/peltzman-
effect.html](http://gregmankiw.blogspot.com/2006/07/peltzman-effect.html)

------
jheriko
i was slightly stunned that this is not common sense: "experiments show that
humans are really bad at judging the speed of an oncoming train at a crossing
until it's nearly arrived" if you've ever seen this at e.g a train station
even, is painfully obvious that your perception of this is terrible - trains
in the distance look really slow.

level crossings have been very common here in the uk for a long time... open
crossings are the exception rather than the rule, and you have to go far out
of your way to find them.

------
BasDirks
"— We're all basically idiots when it comes to merging."

We know.

------
mrThe
[http://www.youtube.com/watch?v=r7_lwq3BfkY](http://www.youtube.com/watch?v=r7_lwq3BfkY)

------
joshdance
Can't wait for self driving cars. And the Hyperloop. And teleporters.

