

Study: Traffic lights should respond to cars, not the other way around - JangoSteve
http://www.sciencenews.org/view/generic/id/63481/title/To_tame_traffic,_go_with_the_flow

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krschultz
Not to sound like a radical libertarian but imagine a world in which roads
were operated with some sense of incentives to actually MOVE TRAFFIC THROUGH.

Lets have Tolls - but you get a refund when you are delayed. I imagine
construction would suddenly be done 24/7 and be finished in half the time.
Traffic light systems would be heavily automated/AI so that there isn't much
traffic.

Instead they give out construction contracts to the "cheapest", which ignores
all of the wasted time and gas the public endures in traffic, a secondary cost
of the project.

~~~
njharman
Almost every place I've lived in the US construction does occur 24 hours, but
maybe not 7. Commute and daily traffic require it. Maybe you're just not out
24/7 to see it?

Most traffic systems are automated and their goal is to MOVE TRAFFIC THROUGH.
The minimal use sensors in the roads to help determine when to switch lights.
The most advanced are integrated and use many metrics and algorithms in
controlling traffic signals <http://trafficinfo.lacity.org/html/atsac_1.html>

~~~
snarkyturtle
While their goal is to MOVE TRAFFIC THROUGH, they move it in the worst
possible way. Ask any traffic official, they program the system to limit the
speed of the vehicles, rather than help them find the most effecient. This
"safety feature" leads to exactly what the article cites: stop lights that
inhibit someone from going too far without stopping or at least slowing down.

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SeanLuke
A sort of vague way to do the green wave, but okay I guess. But -- and I say
this in all seriousness -- one of my PhD graduate students had a far more
interesting and elegant technique five years ago.

In short: each car has a piggy bank. As you're sitting at a red traffic light,
it dispenses tokens into your piggy bank. When you go through a green traffic
light you have to give some tokens back. Here's the catch: when deciding who
to give the green to, a traffic light awards the green light to the compatible
set of lanes which have cars with the most total tokens. [Also: tokens expire.
And emergency vehicles can be given infinite tokens].

Thus if you've been waiting at a zillion reds, you'll accumulate enough tokens
to force your way through green lights later on. The idea is to spread the
pain.

<http://cs.gmu.edu/~sean/papers/aamas06-traffic.pdf>

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brc
It's a good idea but would really require the car to have interaction with the
system, or the system to read and interpret individual cars (to assign the
token).

I think the advantage with the system shown is they are only measuring
throughput rather than keeping tabs on individual cars. Thus I assume it's an
easier problem to solve.

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SeanLuke
Well yes and no. Our proposal wasn't to keep tabs on cars. There's no tracking
whatsoever. Lights have no idea of knowing where you have been or who you are:
you're just telling them how much pain you've been suffering in the near past.
The tokens aren't marked -- they're simply currency so to speak.

The approach does require two-way communication between cars and nearby
traffic lights. But the approaches that various people are suggesting,
including this article, largely rely on communication as well: just one-way.
The lights generally need to be able to detect cars approaching and at quite a
distance. This requires the cars announcing their presence: either the lights
have a sophisticated sensor system ( _lots_ of plates in the road, or a vision
system) or -- more likely -- the cars need to have beacons installed which let
the lights know they're coming. A great many of these methods also benefit
from knowing not only that cars are approaching but where they intend to go --
are they going to turn left or right or straight -- well before they get into
their lanes. This requires additional signaling.

What Gabriel Balan picked up on, is that to make the system fairer _and_ more
efficient, you need to be able to transfer historical information from light
to light. Not only information about how many cars are coming, but what their
previous histories were. If you don't want the lights communicating with one
another -- essentially tracking your car -- you can do what he did: have the
cars build up a history on their own and relay that to the lights as they
approach them.

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brc
I understand what you're saying. I think in your design you can keep it
essentially one-way without needing anything on the car. This could be done by
reading the plate and assigning it to the system, which would then allow
tokens to be added/subtracted on the system side only. This does, however,
mean that all the traffic lights are hooked up together, but still this is
much easier than asking that all cars be modified.

The congestion charging system in London works in a very similar way - it
doesn't pretend to know when a car is going to come in or out - just reads the
plate and stores it in the database.

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points
Radical, but there's only one word needed here.

ROUNDABOUT. Build some.

~~~
kes
I live in a small midwestern town that has recently taken to the idea of
roundabouts. At first, I was extremely pleased (having good experiences with
them in Paris/French HW systems) but I quickly became discouraged when I
realized that 90% of drivers had no idea what they were doing.

I now avoid certain routes through town because I'm afraid of getting in an
accident.

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eru
What's so hard to get for those people? Roundabouts seem simple enough to me
(though I may be biased, coming from Europe and now living in Britain).

~~~
blaines
The roundabouts near me seem to be working well...

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jacquesm
In plenty of countries this is a reality already. Sensors are placed anywhere
from a few meters to hundreds of meters ahead of the actual lights to
determine the flow of traffic, there are 'green waves' which you can
synchronize with to guarantee uninterrupted passage (both for congestion
control and to save fuel) and there are adjustments made based on the expected
flow from different routes depending on the time of day.

The future, in this sense at least, has already arrived.

Sure there are plenty of places where this is not common yet, but
infrastructure upgrades are expensive.

~~~
WalterBright
The wire sensor buried in the pavement has been around since the 1960's, and
nothing has improved since then.

You don't need to place sensors anymore, a simple camera can do it.

~~~
jacquesm
It's a bit more involved than that, nowadays there are many sensors instead of
just one to detect a waiting car in front of the light, the speed gets
measured as well as the number of vehicles.

As for a 'simple' camera, nothing that you deploy in all weather conditions is
ever simple if it is to operate reliably.

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alecco
Getting rid of cars as much as possible in congested areas is the best way.
Promoting very good public transportation and prioritizing people walking and
riding bicycles.

If they optimize the flow of cars in a little time there will be more people
using cars in those areas and no operations researcher can solve that bigger
traffic jam. People, like any biological entity, adapt to the environment.

~~~
sigstoat
buses, trucks, emergency vehicles, bicycles on the roads, taxis, people going
places too out of the way for public transportation to service and whatever
other uses of the roads that aren't immediately obvious would all still
benefit from this.

smoother traffic flow and reduced time on the roads would also reduce
accidents, which would require fewer vehicles be manufactured, which is a
nontrivial environmental impact in and of itself. oh and fewer humans would
die in horrific accidents.

~~~
sgibat
plus it will be easier to integrate the infrastructure when cars go automatic

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ErrantX
"Traffic lights should respond to cars, not the other way around"

True, but believe it or not it is incredibly difficult to get right.

I'm on my local council and we recently did some prep work to look into adding
"AI" to the towns traffic lights.

Here is the problem; you have to do a significant portion of the lights - or
it actually gets worse. A stupid amount of planning goes into light sequencing
(at least it does here....) on a macro-scale - so all of the towns lights are
pretty much synced to optimize traffic flow as much as possible.

Imagine doing that on the fly for the entire town.

What ''has'' been suggested, and looks good, is a sort of hybrid approach -
where traffic levels are monitored and a number of different optimized
sequences used to clear traffic jams as appropriate. Even this is a pain
because it is essentially the same as replacing the towns system three or four
times over :)

And we are lucky in having a medium sized town with large areas of uninhabited
farmland (read little traffic) around it.

Not that it isn't a good idea - but I don't think it is a very simple option.

~~~
cliveholloway
And let's not get into "intelligent pressure pads". The number of times I've
had to run a red light at night because the pad doesn't register my bicycle...

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blaines
Where I live there are roads to nowhere and traffic lights in quiet
neighborhood intersections. I'm not sure who 'engineered' the streets, but one
car can stop a swarm of traffic, and the speed limits are many times
ridiculously low i.e. 35mph on a two lane street in a non-residential area,
high visibility, and no intersections within 2mi.

This is a broken system in which much of my time is wasted daily, and the
"green wave" is not the system's goal. It's nice to see some people
experimenting to find better ways to regulate traffic. It should be obvious
that 90% of the time the current flow is not the calculated daily average.

After all, Since when do 50,000 cars/hour drive on a street at 2am?

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shotgun
If I had a nickel for every time I was at a stoplight and thought the same
thing...

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justlearning
even better: here was someone who tried to change it for good:

<http://en.wikipedia.org/wiki/Hans_Monderman>

<http://www.wired.com/wired/archive/12.12/traffic.html>

there is also a brief interview on youtube with him explaining his theory of
change.

~~~
metellus
The only reason his intersections are safer is that the lack of signage makes
drivers uncomfortable and therefore more careful. Get rid of signs everywhere
and that discomfort goes away.

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nollidge
Surely they mean "Traffic lights should respond to cars, AND the other way
around?" The lights aren't really necessary if nobody's responding to them.

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sprout
Shouldn't lights be optimized first to reduce accidents? I've always
understood inefficiency to be an intentional safety feature.

~~~
Empedocles99
Keep all lights red.

Nobody moves, pretty simple heuristic solves for reducing automobile
accidents.

~~~
sprout
Maybe the ideal is that there are signals that permit bicycles and
pedestrians, but if cars want to go they have to get out and push a button to
get the light to let them through.

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swah
Well, then just remove the lights and go back to cars responding to cars.

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Tyr42
I do remember there being an article on here about just that. It seems to have
some success.

Also: Roundabouts.

Edit: I guess I should read the two links that I open in background tabs
_before_ posting. Now I feel like a fool.

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sliverstorm
If they remove timers from lights entirely, they better improve the sensors.
There are already numerous lights that do not detect the presence of my
motorcycle.

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bokchoi
When I'm riding my bike and I need to turn left, I'll jump up and down on the
sensor. I look like an idiot, but usually it works! ;)

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marcinw
Why not just buy a neodymium magnet? This usually does the trick to trigger
the sensor.

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pak
Then one day, you kneel down to check your engine oil, and bam, there go all
your credit cards. There are downsides.

I'd prefer if they just made the loops a little more sensitive. A 200 lb piece
of metal would seem to suffice for a true positive...

~~~
kijinbear
Seriously, anything except a pedestrian should trigger the sensors. Car,
motorcycle, bicycle, wheelchair, or a freight train from your subconscious
trying to crush everything in its path... whatever it is, if it's sitting in
front of an intersection and it's not on the sidewalk, chances are it's
waiting for the green light!

Sure, you might get a false positive from time to time, but whatever causes
the false positive probably shouldn't be in the car lane in the first place.

~~~
njharman
With sensitivities that low false positives are triggered by cars in other
lanes. Induction loops are very sensitive to variations. Believe me, I spent
many hours on tweaking detectors.

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tibbon
As a motorcyclist, I'm going to disagree completely if the standard technology
that is used to detect cars is used. Generally there's some sensor in the road
that detects a large metal object above. If you're riding a 400 pound
motorcycle, it doesn't trigger.

I've sat at lights for several cycles trying to get a left turn signal, only
to be required to run the light (illegally) to get through while traffic built
up behind me. Not cool. They need a better way of sensing cars.

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JulianMorrison
Also for pedestrian crossings, tear up the button controlled lights and put in
a zebra crossing. Those are so much faster. No need for the pedestrian to wait
(nor scramble across in a panicked hurry, if they are old or disabled), no
timer keeping the cars waiting after the pedestrian already crossed, and no
pressed buttons which operate the lights after the pedestrian has gone

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ulvund
Here in Denmark a lot of traffic lights respond to road sensors.

Another cool thing is the countdown in seconds for the pedestrian lights.

~~~
csl
Those metal detectors 6 feet from the light post? This system seems to ensure
that entire _columns_ of cars can flow nicely through _several_ intersections.

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runT1ME
The city I live in doesn't have any of it's lights on timers...Every
intersection I've come to has sensors...

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AndyKelley
Too bad our government is too big and slow to actually do it.

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evo_9
I think it's more a matter of the money the government makes off of tickets
and such. That's the biggest obstacle - the revenue that is impacted by this
change.

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buss
Here in downtown Seattle the traffic lights are timed for pedestrians. One can
walk from one end of the city to the other without waiting for a light to
change.

