
Green Wave - davidmckenna
https://en.wikipedia.org/wiki/Green_wave
======
alamortsubite
To help pay for tuition, one summer I drove a university shuttle in the
evenings after finishing my work-study job. At that time, the lights on Walnut
and Chestnut streets in West Philly were set up with green waves. The best
place to ride the wave was obviously at its tail, entering each intersection a
little before the light would turn yellow. Traffic there was light-to-none,
and its flow far smoother and safer than at the front, where there were
usually drivers pointlessly fighting to maintain their positions. I would
watch them all just up ahead of me, wastefully approaching each red light far
too fast, braking hard until it turned green, then rapidly accelerating to the
next, repeating this insane processes intersection after intersection for a
dozen blocks at a time, like some sort of mobile psychology experiment gone
wrong. Because I was naive, I thought poorly of Pennsylvania drivers.

Later I moved to SF and experienced the same thing on Franklin and Gough, and
realized the phenomenon was probably fairly universal.

Green Waves could be a great thing, but there's still the unsolved problem of
human beings behind the wheel.

~~~
maest
I think this phenomenon shows the importance of communicating to the drivers
that a green wave system is in effect.

You can't really fault people for driving myopically if they don't have high
level information.

~~~
alamortsubite
That might work, though few drivers in the U.S. heed speed limits even in
construction and school zones, where there are typically large brightly-
colored signs and flashing lights and the stakes are much higher.

Also, since the bad behavior on display at the front of a green wave is
pervasive in pretty much all traffic scenarios, it seems like a modicum of
driver training might ultimately be the most foolproof approach.

~~~
maest
With the risk of sounding cynical, I think drivers will be much more receptive
to being told "you can get home faster if you follow the rules" than being
told "you're increasing the risk of getting into an acceident if you don't
follow the rules"

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sjmulder
The town where I live (in the Netherlands) has green waves for cyclists. It's
lovely to experience and also a good way for the council to encourage this
sustainable, healthy mode of transport.

~~~
acidictadpole
That's really cool. Though it does seem to remove almost 50% of the benefits
listed in this entry, but those seem to be focused on fuel-consuming vehicles
rather than bikes.

~~~
lkbm
If it gets more people to bike instead of drive, it still has those benefits.

~~~
acidictadpole
You're absolutely right. I didn't think about it like that, thanks.

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tomphoolery
This is why I always took W Passyunk Ave coming home from work when I lived in
South Philly. If you travelled at around 20-23mph, you'd hit green lights from
the moment you got off the highway to the street you had to turn on. It was
great, but since nobody knew about the concept you'd have a lot of people
frequently stopped in the middle of the street or not moving at the right
speed. I wish this was more common so it would be taught in driver's tests or
something, that way people would drive slower in these areas and also get to
where they need to go quickly.

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ivanech
Great Highway [0] in San Francisco is my favorite example of this. If you
drive precisely 35 mph, you'll hit green lights for about two miles. This
works in both directions. I think it's possible because the lights are to
allow pedestrians to cross the road, so there are no intersections with cars
for the full two mile stretch. Still, I think it's a lot of fun.

[0]
[https://en.wikipedia.org/wiki/Great_Highway](https://en.wikipedia.org/wiki/Great_Highway)

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GistNoesis
This one sent me quite down the memory lane. Back in 2009, I realized a fake-
iphone app pitch where the goal was to sync your music so that you can ride
the green wave as a pedestrian. The music will slow down or accelerate so that
by walking to the beat it guarantees you that you will go with the flow.

As it was just for a pitch, I realized a video (with the help of a friend
checking for my safety) to showcase the usage : Two long-sequence shots of
walking between two places in Paris and being sure to have only green lights,
like 15 green lights total to be nailed when they are clearly not synchronized
for you and there is people and traffic around.

It was an experience in the spiritual line of Claude Lelouch "C'était un
rendez-vous".

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PaulBGD_
Taking Portland Ave and Park Ave are great in Minneapolis, but I agree about
cars in the front speeding, slamming on their breaks for the red, the going
again. I wonder if there should be a new sign for green waves, or maybe we
could just make them more popular.

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cafard
It used to be that an MPH or two under the speed limit would get one halfway
across Denver without stopping for a light. That was a long time ago, though.

I don't drive much these days. In Washington the traffic levels can be such
that the best timing in the world won't set up a green wave. On the other
hand, I do manage now an then to make it half a mile or so as a pedestrian
without stopping for a light. (On 16th St. NW from U to Scott Circle, a
saunter will hit all the lights green; a fast walk might do the same, but I
seldom bother to try that.)

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quartz
NYC has a bunch of these on most of the avenues that break down at rush hour
but work pretty well at other times, especially on weekends when you can do
miles at a time.

You can actually watch the downtown wave approach and pass when you're going
uptown on Park Ave starting around 60th St (and you'll get to watch it many
times as you constantly hit red lights since you're fighting the wave).

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papreclip
On my previous commute home, the green wave seemed to only work if you
travelled 85 or 30 mph (posted limit 55), everyone else got hit with every red

~~~
lkbm
Were you travellng the opposite direction of most commuters? Green wave only
works in one direction.

fwiw, that's one benefit of one-way roads -- they each can be programmed to
ensure a green wave for all cars on them. I never understood why you'd want a
one-way road (outside small neighborhood streets) until my friend pointed that
out.

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Brendinooo
I always appreciated this on the University of Pittsburgh's campus, and was
really happy when they did it in my current hometown.

I used to take back roads and take my chances with speeding and stop signs,
but now I find myself taking the main road way more now because I know I'll
probably only stop at one light maximum, and I know how to time my driving.

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aaroninsf
Two green wave examples I value in San Francisco:

1) the Valencia bike commute green wave (named as such with posted speed)

When it's broken for some reason it's very noticeable and unfortunate.

2) the various coordinated designated auto throughways which make up for the
lack of in-city access freeways

Except when you're going against the direction, like when my wife was in
labor. :|

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tus88
I live in a city where the traffic engineers are too stupid the understand the
value of this...about 50% of the time I get a green light, only to immediately
see the next light go red about 100 meters away. It's infuriating.

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acheron9383
Folsom street in the Mission District of SF has one at 15mph. Perfect if you
are on a bike. Keeps the average speed of drivers down in the residential
areas, and if you know the timing is at 15mph, you might as well just cruise.

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jcrawfordor
My city has posted signs indicating the "green wave speed" in a few spots and
it actually seems like a more effective form of traffic calming than speed
bumps or forced turn obstacles.

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sjlogan
Best green wave I have ever experienced is going north on 10th ave in NYC. You
can drive for 100 blocks without stopping if there isn't too much traffic and
you time the lights correctly.

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dsego
These don't work in my city because everyone just rushes to get to the lights
first and come to a full stop. Then those stopped cars take their time to
speed up again.

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kakuri
Sadly, our green wave is synchronized with a 50 mph speed, but the posted (and
reasonable) limit is 35 mph.

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sixothree
My city has lights timed to ensure that signals turn red just before the wave
of traffic reaches it. You can see the signals have antenna on them pointed at
the next intersection.

It is infuriating on a level I can't describe. My guess is they are trying to
reduce accidents or they are trying to make more tax money by getting people
to burn more gasoline.

~~~
alamortsubite
Do you have a source for this? Driving in city traffic can be frustrating, but
I wonder if the antennas you see are for emergency vehicle signal preemption,
or serve some other purpose.

~~~
sixothree
Lastly, the emergency vehicles use pulsed light which have a different sensor
pointed towards the traffic and not the other direction.

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izzydata
I only ever experience red waves.

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stoltmeister
Love when I get these. Give me more!

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daveslash
Obligatory XKCD Reference

[https://xkcd.com/277/](https://xkcd.com/277/)

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throw0101a
Remember folks: lights timed for 40 are also timed for 80. /s

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ambrop7
Suppose the the period of lights is equal to the time expected to move from
one light to the next, and each light is red/green for the same amount of
time. You have a green wave if you pass the first light green and drive at the
expected speed. But if you drive twice as fast, you reach the second light red
instead of green. Now it would work if the period of lights was half the time
expected to get from one light to the next, but why would that generally be
the case?

Actually I think the opposite will usually hold: you will still have a green
wave if you drive at the expected speed divided by an integer.

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GrayShade
> In the UK, in 2009, it was revealed that the Department for Transport had
> previously discouraged green waves as they reduced fuel usage, and thus less
> revenue was raised from fuel taxes. Despite this government Webtag documents
> were only updated in 2011. It is still unclear if the economic appraisal
> software used to apply these guidelines has also been updated and if the new
> guidelines are being applied to new projects.

Lovely.

~~~
axaxs
Right? Every fiber of my body screams "JUST INCREASE THE TAX!". Figure out the
fuel usage drop, if any, and adjust the tax accordingly. Hell, I'd pay double
fuel taxes if I didn't have to fight red lights anymore.

~~~
sneak
Tax revenues won’t be very helpful when there are mass crop failures and
hundreds of millions starving or thirsty due to climate change.

This isn’t about money, it’s about the inherent shortsightedness of and
staggering destruction wrought by bureaucrats of any country when they are
given incentives of any kind. See also: private prisons, snake/rat bounty, et
c.

