
Smarter programming of stoplights could improve efficiency of urban traffic - meneses
http://phys.org/news/2015-03-smarter-stoplights-efficiency-urban-traffic.html
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WalterBright
With all the image processing cameras out there, and the cameras already
mounted on the traffic lights, it boggles the mind that nobody is making
traffic light controllers that optimize traffic based on current conditions
and a cost function.

For example, if 5 cars are coming from one direction, turn the light red for
the 1 car on the cross street.

I'm pretty fed up with the light perversely stopping the 5 cars at the last
moment to let one car, that is already stopped, enter the intersection from
the cross street.

I wonder how much gas and congestion can be saved this way.

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slayed0
While this sounds great on paper you have to remember that traffic signals are
absolutely mission critical components to the traffic system and what you are
describing pushes them to the cutting edge of what many might consider
"experimental" technology. There can be no trial and error.

Also remember that traffic systems are not developed by start ups that can
iterate quickly with seemingly endless funding and/or no overhead. These
systems are usually under the control of municipalities that are already
strapped for cash and certainly do not have elite teams of developers at their
disposal.

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Cshelton
While traffic lights are mission critical, we can absolutely make it fool
proof, the first time. It's actually not very difficult.

Don't forget, many lights right now are using weight sensors in the ground
(SEE EDIT-2), A. that is very costly, B. They are prone to damage...a lot of
the time, and C. with current technology in cameras, I'd say they will be more
reliable and give better information about on-coming cars from all directions
to the traffic light.

It is quite simple to say, if the conditions are bad for visibility, or the
camera is inoperable, or even a bird is sitting in front of it, whatever it
is, the simple fall back can be 'dumb'. A timer. As they have been for many
many years.

I've thought about this a lot and imagine in the future that each intersection
will actually be able to communicate with the on board systems of autonomous
vehicles and create a very efficient system. At that point, many intersections
would not even require vehicles to stop. It would regulate the speed of each
vehicle so each one could go through with minimal energy impact. ...Sure...it
might be a 'close your eyes' moment...but regardless, we can make it safer
than how it is today...with humans making the stop/go decisions.

Whatever upgraded systems in traffic lights we move to, we have to start
thinking about autonomous driving. It will be a HUGE leap forward in not only
getting around efficiently, but getting around quicker! Human driving
tendencies are inherently inefficient. The slinky effect on roads and highways
is quite annoying.

EDIT: Another 'efficient' thing we can do is place short range charges into
the ground near the stopping point at lights. This is down the road when a
majority of cars on the road are fully electric. But as the vehicles sits at a
light, it would charge. The power would be obtained through using photocells
on the surface, so when a car is not currently waiting on top of it, they are
building a charge. This of course would require the price of batteries to go
way down to be feasible, but essentially, all forms of consumer transportation
will be powered by solar.

EDIT-2: I'm wrong about weight sensors, I actually did not know about
inductive loops at lights. TIL. Either way, they have a limited range of
detection.

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genericuser
Certifying and proving such a system was actually fool proof would be quite
costly though, as in house certification would probably not satisfy safety
regulations.

Side note: most lights use inductive loops not weight sensors for vehicle
detection.

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Cshelton
Oh I agree. Building a prototype and proof of concept alone would go along way
to getting more on board.

I think the biggest challenge though is getting municipalities to replace
current systems. They have already invested millions and millions to get the
current traffic system up. It would almost have to be the next cycle of
traffic lights, when the old ones get replaced (depreciate fully). And of
course, cities would probably want to do their own independent
testing/study...

It would be sweet to start seeing them appear on new construction though.

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heydenberk
It's a neat thought, and everyone who's watched a light turn red ahead of them
just as they cleared a green has thought it before, but there is a serious
downside. Urban stoplights should be optimized for the safety of non-motorists
(pedestrians and cyclists) above all else. Giving cars more uninterrupted
travel leads to higher speeds and more collisions. I'm happy that where I live
there's more attention paid to traffic calming and bicycle infrastructure than
motorist travel-time optimization.

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grapevines
>Giving cars more uninterrupted travel leads to higher speeds and more
collisions

Not necessarily. In a well-timed system, cars that travel the posted speed
limit are indirectly rewarded by not needing to stop. Going too fast or too
slow would mean you would be out of sync with the timed system.

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3minus1
Virginia currently uses smart traffic signals:

> Traffic-responsive signals vary the timing of the lights according to the
> amount of traffic. They use sensors to detect the number of vehicles on an
> approach. The time the light stays green adjusts to let as many drivers as
> possible through before the signal changes to respond to traffic coming from
> another direction.

Back when I lived in NoVa, the lights near me had this and it was awesome

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WalterBright
Lots of lights have inductive loops to detect cars, but they are too close to
the lights. The cars have already stopped by the time the loop detects them.

How does the Virginia system detect the cars?

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count
The VA system detects how many cars are waiting to ensure that as many as
possible make it through in a cycle (up to a limit), not detecting them as
they are inbound to keep the light green.

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WalterBright
That's a familiar system, but it requires a car to come to nearly a full stop
before the sensor picks it up. This leads often to the lights alternating so
out of phase it produces the maximum delay for both streets.

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jakejake
I sometimes get the feeling that traffic signals in my home town (Chicago) are
designed to maximize ticket and speed camera revenue, rather than improve the
flow.

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basseq
> I sometimes get the feeling that traffic signals in my home town (Chicago)
> are designed to maximize ticket and speed camera revenue, rather than
> improve the flow.

You get that feeling because it's true:

[http://www.chicagotribune.com/news/watchdog/redlight/ct-
yell...](http://www.chicagotribune.com/news/watchdog/redlight/ct-yellow-light-
timing-met-20141223-story.html#page=1)

~~~
ams6110
The hidden cost of living in a bankrupt city (and state).

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j_s
Startup opportunity: micro payments to change the light green in your
direction ASAP. Voice-activated bidding with a floating fee that everyone
sitting at the light can contribute towards.

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ChuckMcM
There is an interesting side effect here. Autonomous learning.

Basically when the stoplights in my city switched to a 'three program' light
(they have 'normal workday', 'normal non-work day' and 'commute' patterns
available it means that people who drive "on autopilot" start having the wrong
thing anticipated when they are sitting at the light, (for example expecting a
left turn signal to go green before oncoming traffic gets the green, or
expecting turn signals to activate before through traffic) and that leads to
some interest effects. Most notably people "jumping" into traffic when their
anticipation is incorrect.

The other thing that this does with non-native/less well trained drivers, is
put them in lose-lose situations. I got out and talked to a guy who was
sitting in a non-left lane (it was one lane over), waiting for the left turn
light to activate. I explained to him (he barely spoke english) that from the
lane he was sitting, the left turn light would NEVER activate and by sitting
there while the light in front of him was green he was at risk of being hit by
a car. He had no clue. It was very sad.

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joe_the_user
This seems like a nice idea but I actually think it would be terrible. The big
discovery recent-ish is "Traffic Expands to Fill Available Road Space" [1]. A
situation where traffic lights become smarter to keep traffic balanced between
main streets and side streets and between different intersections of the city
would just mean result in every single intersection of a given city being in
grid-lock simultaneously rather than just some of them.

Already, I've notice that rush-hour lights seem to tuned to take longer than
mid-day light - assume that's because any light-change is going to be
inefficient (logically enough). But since rush is fated to total congestion
anyway, the result just congestion plus tortuously long lights.

[1]
[http://www.culturechange.org/issue8/traffic%20expands.htm](http://www.culturechange.org/issue8/traffic%20expands.htm)

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shijie
Or, we could use roundabouts[0]

[0]:
[http://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm](http://www.wsdot.wa.gov/Safety/roundabouts/benefits.htm)

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ams6110
Roundabouts are OK but they don't work so well on multi-lane roads. The multi-
lane roundabouts I've seen are confusing to most motorists and tend to slow to
a crawl. The problem is there is limited space to change lanes once you are on
the roundabout, so you have to enter in the proper lane based on where you
want to exit. Inevitably there's someone who didn't use the proper lane and
everything clogs up while they stop and wait for a gap in the next lane (which
happens rarely because roundabouts promote continuous traffic flow).

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Cyph0n
They work fine here for 3 lane roads. The issue is high traffic from more than
one direction simultaneously.

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nerdy
Highway commutes will be significantly streamlined when merges are done in a
perfectly interlaced fashion with autonomous drivers. Anyone who has tried to
get on the highway in the US during rush hour probably knows exactly what I am
talking about.

Imagine driving on roads where all the vehicles followed the rules _and_ you
didn't have to pay attention _and_ the road system worked with the vehicles to
improve efficiency.

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arasmussen
I would love to see this implemented in SF. Every day I drive I see one light
turn green just as the next one turns red. You really can't do much worse.

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allochthon
Note that some cities optimize for driver _inconvenience_ , to discourage
driving through the city center.

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vinchuco
If you want to minimize traffic, instead maximize the number of people
transported per vehicle.

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kwhitefoot
It would be even better to minimize the number of people transported.

