The Strange History of Stoplights

Traffic signals are one of the most recognizable - and life-saving - things on the road. But where do they come from, and how do they work?

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Episode Transcript

Speaker 1 (00:02):
Go behind the wheel, under the hood and beyond with
car Stuff from house stuff Works dot com. I welcome
to car Stuff on Scott and I'm Ben. We are
here with our super producer Noel green Light Brown. And
you know what that means, ladies and gentlemen. Wasn't it means?
This is car stuff? Oh yeah, of course it's car Yeah,

(00:23):
that's right. And green Light Brown by that that's a
funny name. Yeah we uh we That nickname actually came
about in a moment of inspiration because you know, Noel
is a man of many monikers, right of course, and
that's one of the reasons that we work so well
with him, because you and I used to have quite
a few uh a k s. Yeah, you know, we've

(00:44):
been getting a lot of those recently an email as well.
Some people have I don't know have we talked about
that in the past, like send in some or something,
because we have a while ago. It seems like recently
we've had this huge group of emails that have come in,
you know, from listeners that have some nicknames. I I
appreciate them always because they're really funny. Yes, pretty great.
We have to wake those on the air, very clever

(01:05):
so yeah, keep doing that, and you know we'll try
to come up with some them on our own here
as well. Yes, so this nickname green light brown. We
were I was waiting at an intersection. And if you
are a commuter who drives in a crowded area ever right,
then you are familiar with the weird the weird thoughts

(01:28):
that come to you while you're just waiting in a
red light. You know, the radio could be on or off,
and you're you're looking around, who's that? What are they doing?
Sometimes you have an awful long time to wait as well.
Oh yeah, to the point where you think, is that
red light broken? Which is something we will talk about
later in this episode, because today, ladies and gentlemen, we're

(01:48):
talking about traffic lights. Yeah, traffic lights, traffic signals, traffic lamps, uh,
traffic semaphores. We're gonna talk about all this stuff. I mean,
there's a lot of different names for these, um traffic
control signals, whatever you have to call it. I always
feel awkward. I think there was an episode recently where
I was saying traffic signal or traffic light, and to me,
it just didn't sound right for some reason, and I

(02:09):
kept second guessing myself. But there's all these different names
for them, and all it really comes down to is
a traffic control system that really, when we go back
in history, we find that it just replaces the policeman
at the intersection, right. And just an interesting side note here,
in some other countries there are still human traffic directors

(02:30):
that will stand there and direct traffic with hand signals,
similar to the way that someone would help a plane
land on a runway. The country I'm thinking of, of course,
is North Korea, which is um you can still see traffic,
human traffic people directing cars in the capital city of

(02:51):
that country. Do they wear white gloves? I think they do.
I think they have a uniform. They're all women and
they have UM if I if I recall, someone correct
me on the I'm if I'm off here, a blue
and white uniform and then like a you know, like
a baton thing. You know, I can picture this. It's
I may have seen this in the past, but it
just seems like a crystal clear image. And that's why
I asked about the white gloves. Um It's it's a

(03:13):
weird thing to ask, but that's where visibility. You can
see what they're what they're motioning. And that's the way
that it used to be all the time at every
busy intersection in every busy city, right you know. And
you know, of course there are other ones where they
would just let them go. I mean you know that,
you know, but in the right and down the heart
of downtown, they would often have police officers that were
you know, set to patrol there or to to direct

(03:35):
traffic there, um, for their entire shift. I mean, that's
all they would do. And it would be shorter because
it's exhausting to do something it's very dangerous, um. And
there's always gonna be a place for that. You know,
in the world. There's gonna be sporting events, there's gonna
be times, you know, after work. Here in Atlanta, a
lot of I don't know how this works exactly, but
I don't know if um, you know, companies pay for

(03:55):
this or what. But we find in traffic a lot
of police officers out in the middle of traffic, directing
traffic at you know, critical rush hour times. Um. Let's
say that, you know, like this is a big building
right here. Sure, well I haven't seen this yet here
at this building because we're not the capacity yet but
once we do get the capacity, I'm sure that around
five o'clock every night, there's gonna be a police officer

(04:16):
out on one of the main stretches or you know,
several of the main roads around here, directing traffic in
and out so that, you know, everybody doesn't get stuck
in the building. He allows for a a certain amount
of people to get out at a time, and it
just keeps things flowing a little better than the than
the normal traffic light system would do, because it's not
time correctly when you know, to take into account the

(04:37):
greater influx of people from this building or from whatever building,
or whatever event is happening at the time. Yeah, I
in my head, I call these left turn cops because
they're there to prevent parking decks from being just uh
cluttered with with cars that can't get out because everyone's
trying to make a left hand turn on a busy

(04:58):
street with no light. However, verse since that traffic is momentary,
right or it is it only occurs at a certain
time during the day, it doesn't make sense to build
a traffic light system or to build a new node
in the traffic light system. Really, uh into the larger
landscape of the traffic. So there's this there's this fascinating thing.

(05:21):
I know sometimes and I think this has happened to
everyone listening. But if it hasn't, man, I envy you,
because what we're about talking about is a great feeling. Scott.
Have you ever been on a straight away where you
see like a bunch of lights maybe every two three
blocks right, and then you hit that just that magic

(05:43):
sweet spot where they're all green? Has never happened? Yeah,
it has happened, but it's pretty rare. I mean, if
you're in a city, you know, typically unless you're doing
this on like a Sunday morning when no one's around,
you're not gonna be able to just free flow through
the streets and threat, you know, through the streets like
that without you know, having some kind of obst goals
in the way, whether that's more traffic, it's pedestrians, whatever.

(06:03):
It happens to be someone you know making a delivery
in the in the next building down the run down
the block, um, you know, blocking the lane of traffic
or whatever. You're talking about. Cascading lights right yeah, yeah,
Now that's cascading and the other type is synchronized and
synchronized are the ones that change all at the same time.
So you know, you see a row of lights like
you're talking about, and they yeah all at one time

(06:26):
where they all go green, and you know, that's fine,
it seems kind of cool that it happens that way.
But the frustrating part about it that is you're only
gonna make one or two of those and then you're
gonna get stuck in the next red light. Right, And
there are some other types of course there there's the
dynamic control, which responds to the frequency of traffic on
the road. But but let's not let's get too far
ahead of ourselves, because I think the one thing that

(06:47):
you and I can absolutely agree on is that we were,
uh is overwhelmed. If fair words, Scott, how much information
there is that is that's perfectly fair. And I think
even more, there's there's so much information out there about
traffic signals or traffic lights you wouldn't believe it. I mean,
I didn't think that there was gonna be a whole
lot to this um other than you know, I know

(07:09):
there's complex controllers. I get that. However, there's so much
more to these things than just that, and and not
only that there's different nationwide standards, you know, between what
happens here in the United States that were accustomed to
what's happening elsewhere in the world. You know, the different
light colors, light like patterns that they use, arrangements, arrangements,

(07:31):
that's right, they use uh, pictograms instead of instead of
just standard lenses. Um, there's all kinds of different variation
that going going on here. And I was just I
was just blown away by the amount of information that
we found on this. So I really don't think we're
gonna get through all of my notes here. And and
you know, I do this all the time, and I
was thinking about this today. I'm looking at my notes

(07:53):
and and tell me if you think I'm right here.
Do you remember that scene an eight mile when Eminem
excuse me, Rabbit was on the public bus and he
was writing all of his his rhymes down for the
rat battle, right, and he's writing down it's the tiniest
little print, and it's just packed in and it's every direction.
That's what my notes look like today, And pretty yeah,

(08:15):
they're pretty thorough, man, even for you. They're close, I mean,
and they're packed in so tightly that I had to
use markers the outline sections so I can keep those separate. Right,
It's ridiculous. So we already want to start with this
maybe history. Yeah, let's just walk through the history in
a brief overall. Look, so we know that traffic signals

(08:37):
and of course whenever we look at history, we have
to look at caveats. So let's see it this way.
The first, uh, the first traffic lights quote unquote that
we know of was installed in December of eighteen sixty eight,
and it was right outside Parliament on this place called
Bridge Street, with the intersection of Parliament Street and Great
George Street. And they were installed by a railway guy.

(09:00):
This is a non electric light. It was a gas
lit light to traffic light and um. Kind of strange
in the way that this all came about. But again this, uh,
this was developed or adapted from the railway system where
you know red means stop and green meant go, and um,
they decided that this would be a good way to

(09:21):
you know, deal with this brand new problem that they had.
And uh. And whereas this London, London, in London where
they said, well, you know we've got we're gonna have
some cars on the road we're also gonna have um
carriages maybe at that time. Exactly right. There's pedestrians, there's
all kinds of you know, there's lots of traffic going on.
It's a busy city even back in course. But this

(09:41):
was a problem railways had already encountered for a much
longer time. True. True, true. So they're they're they're using
the same system, the same way of saying, yet it's
okay to go or you need to stop right there
for this, uh, this this intersection, and at the intersection,
the problem was somebody had to manually operated. Yeah, these
were this is I think you already mentioned it before, Scott. Uh,

(10:04):
these were semaphore. This was a traffic semaphore system. Uh.
And a and a semaphore is uh. If you've ever
been riding a train or you've seen a train go by,
a semaphore is um like the little arm, the rectangular
thing that goes up that says either do not go
or continue or caution. And this has been used beforehand

(10:25):
on train systems for a while, so it makes sense
logically for this to be used um in in a
new kind of traffic environment. Right. However, as you said, uh,
this this thing was it had lamps for nighttime use,
right and gas gasolt nighttime use. Very very forward thinking

(10:48):
for its time. Uh. And it was manually operated by
a police officer, Yeah, traffic police officer who was was
stationed at that lamp, who was supposed to reach up
and switch the light around so that people could see
it in whatever direction to travel they were they were
coming from. So, Um, the problem was the use of
this thing was very brief. They didn't use it for
very long. And then the reason is a bad reason. Um.

(11:11):
So we said that, you know, the ninth of December
I think in eighteen eight by the second of January
in eighteen sixty nine the following year, I mean we're
talking like, how that's less than a month. Yeah, that's
less the that's yeah, it's a little bit less than
a month. Uh. And a gas line leaked, Yeah, leak
developed in this thing. I mean I would guess because

(11:33):
of the constant turning and the constant you know activity
at that lamp. And this is awful. Then the the
the gas line leaked and they think, I don't know
if it injured or if it killed this policeman, but
there was an explosion, uh, from this lamp. So that
was the end of the very first, um, non electric
traffic light. But um, so it's very very short. It

(11:53):
was a you know a significant amount of time later
before we finally decided that electric might be the way
to go with these. Yeah, the con sept was abandoned
at least four gas power traffic lamps just because it
looked like such a health risk. It wasn't until uh,
let's see around early twentieth century, nineteen twelve or so, uh,
that a guy in Utah in Salt Lake decides, I'm

(12:17):
gonna try this again, but I'm going to try it
with electricity as the powers. Yeah, and he's still going
to use the red and green. He's not that we're
not up to the point where we use yellow at
this point. Uh. And I think that, you know, the
way that they got around this is that they said
that the officer would indicate that he was going to
switch the light. So it wasn't like just uh, you know,
switched to red real quick and you get a ticket. Um,
it wasn't like that. It was there was some kind

(12:38):
of indication, whether it was blowing the whistle, it was
a you know, an audible you know, just yelling out, hey,
I'm going to change the light or whatever something like that.
And it wasn't long after that that you know, these
copycat systems started to come out and and this is
in about what nineteen fourteen, August of fourteen when they
started to be installed in Cleveland, Ohio and again two

(12:58):
colors red and green, but this one also had a buzzer, right,
and this was this buzzer was the system for warning
for color changes. So if you're barreling down the straight
away there Euclid Avenue in Cleveland, Ohio, and uh, guys,
just for the record, I haven't driven that street. I

(13:20):
don't know if it's a straight away. But anyway, if
you're barreling down and you see you see that you've
got the green signal, but you hear this buzzer, then
you know that it's about to turn red, and that
that's a neat idea. This design also allowed UM emergency
Assistance and first responders to control the signals manually in

(13:40):
case there was an emergency. So we're getting just a
you know a little bit of UM I guess evolution
as we go on your year by year, there's just
they're they're improving just a tiny little bit, like with
the addition of the buzzer and uh you know, okay,
the initial one was going from gas to electric. That's
a huge one, right, but adding the buzzer, that's pretty big.
But in whey, uh, this when we have what is

(14:02):
probably what we could consider the the modern traffic signal.
I mean, this is this is what we all know
and recognized. And this is the first four way, three
color traffic light that was installed or created rather by
a police officer named William Potts in Detroit, Michigan in
n Yeah. This this is a big thing because it's

(14:22):
it's a four way, so it's mounted at the center
of an intersection, and it's a cylinder with uh or
excuse me, it's rectangle four sides right, and you have
you have three colors on each side in the same pattern. Right,
You've got the you've got the red at the top,
the yellow in the middle, and the green at the bottom.

(14:43):
And again this is manually operated. So can you imagine
the difficulty of operating twelve lamps, you know, three in
each direction um from this tower. And that's the other
thing is that this was installed in a tower as
part of a tower. Um, I guess I don't know
if you. I mean when you look at the picture
of this, uh, this this initial tower, this traffic tower.

(15:04):
It was at Woodward and Michigan Avenue UM in Detroit,
and you know, the officer would stand in the tower
and switch the lights. So when we say it's recognizable,
I mean it does have the three lights that it
does have the same idea I guess as a standard
traffic light. But um, look at the tower and you'll
and you'll see that it's it's a way outdated way
of doing things obviously. Um. But these towers then started

(15:25):
to pop up all over the place. Uh yeah, and uh,
these these towers started to pop up, I guess within oh,
let's see about over the next two two and a
half decades or so, there were more than six hundred
intersections in Detroit with these lamps. In the six hundred
intersections with these now, I think in one year they

(15:46):
had something like fifteen towers. So I mean it grew
that quickly. And then as you said, you know, by
by that time, six hundred signalized intersections in Detroit. That's
an awful lot. And this is uh what you said,
you know, that was twenty six years later that this
article that I'm looking at was was written in ninette, right,
and they're talking about you know that that's more than
eleven thousand lamps in service by seven and there were

(16:08):
more than thirty six thousand signalized intersections across the United
States at that point. Yeah, And it's a it's an
interesting um. It's an interesting evolution because it happens so quickly.
And the reason it happens so quickly is because regardless
of how you feel about getting stuck behind the red light,
the fact of the matter is that they save lives.
I don't know if I don't know if driving in

(16:31):
cities would be possible without something like this, you know
what I mean. And we've of course, that's not to
say there are not some places in the world where
driving in the city, even with the light or traffic director,
is still a very very dangerous game. No, no, no,
And you can see clips of that on YouTube. But
but we know that this stuff is still, as we said,

(16:55):
manually operated. We don't see them, we don't see the
first interconnected traffic signal system for a little while now.
Now Los Angeles installs its first automated signals in nine right,
the first non manual Yeah. Sure, but again they're not
interconnected like you're talking about. It's all the way until

(17:15):
about nineteen seventeen when the first interconnected traffic signal systems
were developed. And that was in Salt Lake City as well,
So there there are innovators out there. Yeah. And it
was pretty small, um, the system itself. It was just
six intersections. They were controlled at the same time from
a manual switch. And now we have cities that literally
run out well actually central computer systems that run thousands

(17:39):
of intersections at a time from one central control station.
And if you go across the United States, I think
there's something like I want to say, it's five hundred
individual um, you know, independently operated known traffic control system
operators are operating systems, I guess, and I don't know
if I'm saying that the right way, but they own
proprietary systems that are distinct and different from the city

(18:02):
next to it. Um, And and that becomes a problem.
There's no real real connectivity between different cities. Yeah, I
don't know, is that a problem really? But the thing
is there's no standard. Yeah, there's no standard and having
no standard can always be problematic over the long term,
just like um, just like trying to connect railroad tracks
with different gauges. Right, but we're getting track. I didn't

(18:23):
mean to do that. I'm sorry, but let's let's carry
on with just a little bit more history before we
get on the types of I hope it didn't cut
you off at all, all right, So to take you know,
this interconnected idea just one step further, UM, they finally
had automatic control of these interconnected lights UM in Houston,
Texas in about nineteen two, so that was just about

(18:46):
five years later. Um. And then there's the first traffic
lights in England finally uh in nineteen Yeah, but we
don't see the first entire traffic signal system of a
computerized until nineteen six. And right now, that is the

(19:07):
closest thing there is to a standard, a computerized system
that is at the very least largely automated. And again
we will talk about these numbers in a little while here,
but again, literally thousands of intersections that are that are
controlled by one central system. I think it's kind of
cool because just the the elaborate organization needed for that

(19:31):
and the calculations required to to make that happen. Uh,
those amazed and befuddle me. But honestly, Scott, you know me, man,
there's still to me. It seems like there's something I
guess chuck from stuff you should know. We call it hinky.
There's something a little bit off about it, because I'm wondering,
why hasn't there been an action movie yet where bank

(19:54):
robbers hack into the traffic light system, make the fast
getaway or stop everybody else in the way, or create gridlock? Right? Um,
you know the Italian job they did something like, they
did it manually. Obviously, they just created a traffic jam. Yeah.
And they did the same thing with the you know,
they did the one in Italy and they did the
one in l a And it was the same thing.

(20:14):
It was supposed to be like the biggest traffic jam
ever in you know, in the world that story. Yeah, exactly, So,
so you know, their manual attempts to do something like that.
But you're right, I wonder why there hasn't been an
action movie that has shown, you know, like more of
a high tech way of shutting down a city. Yeah.
I guess maybe it's just really hard to get into
it or perhaps a lot of people don't know about

(20:37):
how these traffic light systems work. So let's let's see
where do you want to go with this guy. Oh
my gosh, there's so many different places that we could
talk about. Types of lights, we could talk about, you know,
some of the older stuff. We could talk about phases. Um,
there's all kinds of stuff. I mean, and you know,
the basics. I don't think we really have to cover

(20:57):
the basics. I mean, but but but one thing, you know,
one thing I just want to mention. I say this.
I've said this a few times over the years of
car stuff and even high speed stuff. Have you ever
seen a traffic light or a traffic signal sitting on
the ground when it's being serviced, you know, like if
they take it down from the pole or and set
it on the on the concrete next to the road.
They're huge. They're enormous. They're like five ft tall or something.

(21:18):
I mean, they're they're big. It's it's it's very deceptive
how big these things are doing when they're up on
the pole or you know, hanging on the wire that's
wherever it is. You have no idea how big these
things are. But they're massive, and then it gives you,
you know a little bit of pause when you think like, well,
you know, I've been through this intersection before when there's
heavy winds and you see those things kind of blowing horizontal. Man,

(21:40):
that's scary now when you think about it. You know,
if one of those were to come crashing down, they
could do some serious damage. Oh and I'm sure it
has occurred. Oh yeah, and that's why, you know, in
in the hurricane regions. That's one thing that you know,
I found is that uh, you know, places along the
shore the coastline here that are susceptible to hurricanes, they
have a separate set of standards for the way that
these things are you know, um posted at these intersections right,

(22:02):
the metal the metal are right looks like a lower
case hard or even more than that, it's almost like
a like a full structure, like with four corners that
that oh yeah, every single one of them. It's a
very very heavy duty way of putting up. But you
can't just throw, you know, something that's that large and
that heavy on a wire, you know, right outside of
you know, I let's say you're just off a barrier,

(22:23):
barrier island or right, and you're gonna have winds blown
through their ninety plus miles an hour constant. I mean
you can do it, but you have to replace it
every what two years? Yeah, and you know, I mean
just the risk to citizens. That's a very good point. Yeah.
I was, I was being thrifty about it, but you
were being in a humanitarian, responsible civil engineer. Okay, So
we know that, all right. We we talked about types, right,

(22:46):
so let's let's talk about the light itself and then
build up to the overall systems. Okay. So so if
you have one lens, it's called a single aspect, right, Yeah, yeah,
just the basic stuff you think you know, when it's
flashing red, it's a stop sign, flashing yellow, watch out, uh,
flashing green, It can mean a couple of things, depending

(23:08):
on where you're going. I don't think I've ever seen
a single a single lens flashing green stoplight. I think
it might be a Canada thing, man, Maybe I don't know.
I'm not sure if it's a U S thing. But
maybe somebody can write in and tell us, especially especially
those of you out there who take long trips for work,
especially truck drivers, because the you guys will often be

(23:31):
the ones who have the best chance of seeing the
weirdest traffic stuff. Yeah, some of that oddball stuff out there,
all right. So, um, dual aspects are two lenses, obviously,
and typically these are red green, like the old signals
were way back when. And one example I can think
of this is you know, when you're getting on the freeway,
so you know, it's one car per light and it
and it flashes between red and green. There's no yellow

(23:52):
in between. It's just red green, red green, red green,
back and forth in it. Um, that's about the only
example of a dual aspect light I can think of,
unless it's in an intersection where you know, it's typically
flashing yellow, but at certain times a day they switched
it over flashing red. I've seen that as well. Yeah.
Then there's three or more aspects, the tri aspect or

(24:13):
the multi aspect one. And you know that's the one
that you will most likely see, at least here in
the States. That's a lot of other countries. Yeah, that's
the old red, yellow, green, and the old standby and
this the arrangement might change depending on the country in
which you find yourself, but it should be clearly recognizable right. Well,

(24:36):
it's typically the red on top, green yellow in the middle,
of green on the bottom. And you know, because we
talked about that in the uh the street sign episode recently. Yeah,
you know why red's always on top and green is
always on the bottom, excepting that one instance in where
was it New Jersey or it is in New York somewhere. Um,
it was a borough I guess that as a predominantly

(24:57):
Irish community and uh, and they wanted to green on
top of the red, so they got to be different. Yeah,
I guess so, so there is one exception here in
the United States. But um, I think what you're getting
at there is maybe the horizontal mounting too, because you know,
sometimes they mount the horizontally. And just to answer the question,
which maybe have maybe you don't, but I found it interesting,
is that if you're a country that drives on the

(25:18):
right hand side, the green light will be on the
right hand side when you approach that light that is
mounted horizontally. If you drive on the left hand side,
the green light is going to be on the left
hand side. Uh. Yeah, I know, Ben, It's not rocket
science or anything like that, but I felt it was
worth pointing out Anyways, I feel that the first time
I drive on a different side of the road legally,

(25:38):
I mean, I will be uh, I will already uh
be so alert and aware of that kind of stuff
that I might just not even notice somebody just go Okay,
it's green. Probably yeah, I mean, I I can tell you,
I don't even recall seeing any that were horizontally amounted
when I was in Ireland, but there must have been,
and I'm guessing that they were on the left. I'm sorry,

(25:59):
the green light would have been on left. Yeah, And
I guess you just you drove with it. But that
makes sense. The no traffic signals aren't just for roads, right,
we know that they're also for uh like locks on
the Mississippi River, you know, to let you know a
vessels passing through um or that the lock chambers being
empty or filled, uh or if it's green then you

(26:21):
can take your ship through. And if you happen to
be in Canada, then you know if you're you're in
the Providence of Quebec or the maritime providences. The lights
are often sideways, but each one is going to have
a different shape. Now, the red light will be square,
which is you know, it's typically a circle here in
the United States. Um, and they could be in pairs

(26:42):
at either end of the fixture, so that's a little
different as well. And the yellow will be a diamond
shape and then the green will be just a standard circle.
So they've got even different shapes of lenses. In Canada,
a completely different system, which I like the idea of
having a different shape, like a larger shape or something,
because that will help differentiate things, especially for people, you know,

(27:03):
for the few members of the population who are color
blind or color deficient, the pattern of the lights is
very important. That's a good point. I was wondering why
they would even bother with that because we can still see,
you know, that's a red light, that's a yellow light.
What what does it matter what shape it is? But
you're right, it's through a color blind right, Yeah, we're
as a color deficient person, we're just we're dangerous. I'm sorry,

(27:26):
it means that color blind, it's color deficient. Well, well,
technically what I have is color deficiency because I can't
differentiate between um, you know, some some shades of different colors.
But it's not it's not like a black and white
film noir for film for me, your color challenged, right, Yeah,
I like to say color interested. But the only time

(27:50):
that really pops out for me is if I'm at
the optometrist and uh, he'll, you know, hold up the
little here. She will hold up the little circle with
the different color dots and you have to try to
see the number. I don't know what it. I I
know it's seventy six because people have told me, But
I can't see. You cheat on your eye exam. Well,

(28:10):
I have not cheated on the eye exam. I have
been fairly fairly honest about it. Well that's good. I mean,
it's only for your own benefit, right, Yeah. I don't
think you win anything if you cheat on and no
you don't, you do not. But we're getting off track,
and that was that was my bad this time, way
way off track. All right, So so how about this.
Let's talk about the lenses. Yeah, it's just like there's

(28:30):
there's so many little things like this. I think maybe
we should just chip away at all this stuff and
we'll see how much we can get into this episode. Right,
So let's talk about the lenses. There's they they used
typically um fresnel lenses, now fresnel lenses were invented in
the about the eighteen twenties, and we're still using them
in these in these lamps. And I'll tell you why
we're using them, and and that's because it's just a

(28:51):
great design. I mean, it makes perfect sense with with
this application. They were originally developed for lighthouses again back
in the eighteen twenties. And the idea is that the
lens captures more light from a single light source you
know that's behind it, uh, than a standard cut lens would.
Let's say, just have a flat lens. It's not gonna
pick up the same thing as a fresnel lens will.

(29:11):
So it's gonna gather more light and it's going to
direct that light into whatever direction you directed, you know,
be the way that the glass is cut um in
this in this case, it would be towards traffic. And
so somebody can see that lamp. It's it's they're they're
they're cutting a directional pattern so that the traffic that's
approaching sees it more clearly than the traffic coming from
the opposite direction, where lane that is off the side

(29:32):
that shouldn't be looking at that light necessarily, you know,
turn lane light versus um you know, a through traffic light.
So um again, you know it's it's just a smart
way to do it, and and you can see it
from a greater distance because there's more light there. It
just it just makes perfect sense to use this this lens,
even though it's something that's been around for Boy we're
talking almost two hundred years at this point. Wow, this

(29:54):
is one of the nerdiest anniversaries we could throw. Maybe
we should do I wishould do as special celebration possibly.
And you know one thing though, can you can you
remember the first time you saw lenses that had the
LED lamps instead of um, instead of you know, the
the the the old ones that were lit with a
lightbulb behind them, right, yeah, you know. I was just
about to bring that up, because led lenses are probably

(30:17):
going to be the future of traffic lights just from
a cost perspective, the amount of the amount of work
you get out of them versus the higher cost of
the l ed, which is going down and has been
going down for a while. I think it means that, um,
I think it means that the regular, incandest fluorescent lightbulb

(30:40):
traffic lights have their day's numbers. Oh yeah, And you know,
I'll tell you about those in just a second. But
the L E. D S, I mean, they use less power. Um.
You know that they last longer because you know that
filament there's no filam, there is no filament to burn out. UM.
They also, um, they also arrange them in patterns so
that and I know you've seen this already that some
l eds do fail. I understand that. But it's not

(31:00):
just one that's that's powering this whole thing. It's it's
a huge array of LED. So so you know, let's
say that even ten go out in a red or
green lamp, you're still gonna be able to see that
that's a red or green lamp. But you know, there's
gonna be less problem with them burn out, you know,
so that there's no indicator at that intersection. I've had
to deal with that recently a few times on the

(31:21):
way into here. You know, in the downtown Atlanta lamps
on the smaller backstreets, UM, oftentimes you know there's there's
maybe one or two lights hanging so you can see,
you know, what it's supposed to be. But you come
up and there's one that's just empty, and it doesn't
you know, light up at all until until it goes
back up to yellow or red, you know, if the
green is missing or whatever. Man, those are the pits.

(31:42):
And I'll tell you you know that those are the
old conventional lighting systems, the one with bulbs and the
ones that do use bulbs. This is kind of strange. Men,
They use either sixty seven, sixty nine or one dred
and fifteen. What medium based bulbs and medium based bulbs
are just the same kind of light bulbs that you
would use like in the lamp in your house. Yeah,
So isn't that weird to think that that is actually
what is power? And they're pretty low wattage too, and

(32:04):
the seven watch is very sixty seven and sixty nine.
These are very low. Well, I guess they're really dependent
on you know, on the lens and then using you know,
maybe like a mirrored background, like you know, a mirrored
surface or a reflective bowl design that that directs the light.
I mean that was critical for those But man, that
does seem like a low watters doesn't it. And and

(32:25):
also how often you have to replace bulbs in your house.
I mean, if you're turning the light on and off
all the time, it's gonna burn out quickly. Yeah, because
you're you're sitting there. Um, if you think of a
bulb in your house as a traffic light, then just
go stand by your light, switch count two, I don't know,
count off sixty seconds and be fair about it, and

(32:47):
then switch it on for sixty seconds, then switch it
off and just do that forever and see how many
switches it takes. Yeah, I bet it would. It would
burn out super quick. And that's the problem with these
old systems. So so cities are are, you know, quickly
trying to convert over to the LED systems. There's one
problem that they are finding with the LED systems, and
this is kind of a I guess it was unforeseen

(33:09):
at the time. I don't think anybody really thought about this.
But in cities where there's snow, snow and ice, the
l e ED lenses don't create any heat like the
like the incandescence, they can freeze over. They do freeze
over and oftentimes you know, if there's a snowstorm that
you know, the wind is blowing and it attaches itself
to the to the lamp um, you're gonna see that.

(33:30):
You know, the snow actually gathers on the lenses as
opposed to the older, older types where the incandescent bulb
was enough heat to keep the you know that that
lens area free of snow and ice, and you can
still see it through the snow. It's a it's a
it's a faint glow, but it's not a perfect way
to do it. So they're finding ways to to keep
that off of that surface now, right, And hence that

(33:50):
is a new uh, a new item on the bill
too for each of those lights. So clearly the what
what we're finds the evolution of traffic lights is not complete, right,
we haven't perfected it yet, but we're in there. We
have done some really cool stuff, Scott, I want to
talk about how the how the traffic systems know when

(34:12):
to turn green, when to turn red? How how do
you heard all of these cats? In other words, you
know what I mean? What what is traffic light control?
All right? So control of the intersections. This can get
a little bit tricky, right, So this is this could
be um, you know an intersection that is uh and
I'll say it's off the grid. It's yeah, I guess,
so I mean it's one that's you know, maybe on

(34:33):
the outskirts of town that's not part of the central
controlled system, but it can maybe if it's a modern one,
it could be adaptable, and it could be adaptable to
traffic patterns and times a day and things like that.
But more than likely, if it's one that's not connected
everything else, it's likely one that just has a standard
set of times that um, And I don't know if

(34:53):
it's fair to say that it's more than likely that,
but um, the way I picture it would be is
that it's one of the older type systems that has
the big metal box next to it and can be
manually controlled as they wanted to. But typically the way
it runs is that, you know, like you said, sixty
seconds on red, sixty seconds on green. It's like us
on red, sixty seconds on green. Yeah, it's like a

(35:14):
clockwork mechanism. Yeah. And that's that's the old way of
doing it, I guess. And then the new way is
with these modern controllers that sense traffic, you know, and
that's via detection, uh like signal devices. Yeah, I guess.
So I mean whether that's you know, infrared, it's it's radar,
it's microwave systems that that just count vehicles as they
go through, and it says, well, there's a lot of

(35:34):
traffic headed north and south, I'm gonna I'm gonna keep
north and south running freely here, and there's less traffic
coming from east to west. I'm going to I'm gonna
maybe slow that down. So you know that that cycle
doesn't go through quite as often, or that phase doesn't
go through quite as often. And if you're a traffic controller,
that's that's the phrase you use. Use the concept of phases.
And this is a group of movements across various traffic lights,

(35:58):
grouped together. So there might be two phases at a
regular intersection. There's the northwest phase or excuse me in
the north south phase and the east west phase. Okay,
And I've seen this a couple of different ways, Ben,
So I know the way you're describing is one way.
But then other people say, no, one phase is one
individual movement. The other people say, no, it's a it's

(36:19):
grouped together. Like if someone's coming north and south, that's
one phase. They might see it as that's two phases actually,
so uh, it depends on who you see or who's
writing this. You know, whether it's a traffic engineer, if
it's a I don't know, a different type of engineer. Uh,
they might, they might look at this differently. But the
phases can be you know, either vehicular phases or they
could be pedestrian phases. Um, you know, there could be

(36:41):
a you know, where all all signals are read and
they allow what they call a is it a Barnes
dance move? Is that right? Is that what I'm thinking of? Okay,
describe it to give be sure. Okay, here's what I'm
here's what I've I've heard Barnes dance, I think, and
I think that's the name. I'm going to search for
that in just a second here. But um, that is
where all traffic lights turn red in an intersection and

(37:02):
pedestrians are allowed to go not only you know, across
the street whichever direction you know, corner to corner, they're
allowed to go diagonally as well. Oh yeah, also known
as a pedestrian scramble. Was I right with Barnes? Absolutely right?
It sounds funny like barn dance, but but it is.
It's it's almost like pedestrian chaos at some point. Yeah,
and that is a that's an you know, Barnes dance

(37:24):
is an official thing of the name for the engineer.
I think his name is Barnes. It's big in Japan,
is it really, Yeah, it's named after Henry Barnes. Okay, there.
He was the guy who made it popular um back
in Colorado in the forties. And I think Massachusetts uses
that as well. And I've seen people kind of, you know,
illegally doing this, you know that when they must have

(37:46):
studied the traffic, because this is a dangerous move. If
you you're crossing diagonally across a busy intersection in the city,
that's a dangerous move. But if you know that it's
going to be one of these Barnes dance situations or
a pedestrians scramble, just I think it's hilarious, right, I mean,
I've seen that happen. I guess when a you know,
police officer stops all all forms of traffic and lets
that happen. But I mean to have it a controlled stop.

(38:09):
To do it that way, that's really unusual. To have
it be a routine thing. You have to have a
very high pedestrian density in your city. So like so
this I could see working in London and uh Tokyo
maybe yeah, And then again, I mean, just as we said,
these signal controllers are controlling all of this. You know,
the the vehicle, you know, the vehicular phases, the pedestrian phases,

(38:30):
you know, the the intervals of the lights, you know
how long that they remain lit or unlit um, you know,
the the controlled or what they call protected left turns. Uh,
they're controlling all of that. And that's all different phases.
And I think that they're even different different rings within
those phases, which is a completely different bottle wax. But man,
there's there's so much here, Ben, right, I don't I

(38:52):
think we'll get lost in the weeds if we start
to go down the phase path, because that's something you
almost have to see, um a whole chart to understand
what we're talking about. But but you know, some sections,
some intersections can have up to eight phases per intersection,
and then within those eight phases these different rings that operate,
and it really does get complex and without being able
to to visually depict this is difficult. Yeah, and they

(39:14):
loop in with other systems as well. And think of
if we want to use an analogy, think of the
controllers of these traffic systems, the human minds behind this
as these composers of this incredibly complex symphony, right, and
they're arranging things. Uh and and they're they're often unappreciated

(39:38):
by the people who just passed by and hear the music. Oh. Absolutely.
It takes a real talent to be able to uh
kind of lay all this stuff out and make it
have it makes sense. And and then I know that
the systems now are smart enough that they kind of
self adapt once they set it up initially. Uh that
you know, the systems then do kind of take control
of that intersection. Uh. You know, the system says, well,

(39:59):
like I SA said before, it counts traffic. It counts
the number of cars to go through it. Uh, it determines,
you know, via inductive loops below the below the surface
of the street, when a vehicles there and if it
should even um induce that that protected left hand turn
or not. And sometimes I encountered this in the way home.
There's a there's several lights that I know that if

(40:20):
I don't get to the turn lane and I'm not
parked in the turn lane, uh you know, maybe let's
say ten seconds prior to the light on my side
turning green. Oh yeah, then you won't get the signal,
I won't get the left hand turn signal, and and
it's sort of frustrating, but but I just know what
I know to expect it at this point. In fact,
the one that's right outside of my my neighborhood does this,

(40:41):
and it's it's something that you know, I've just come
to understand and I didn't even you know, read about
it or anything like that. You just understand it. After
going through this intersection, you know, one hundred times or something,
you get the feel for what's going on there. Yeah,
I think every Uh It's funny because I think every town,
at least every small town that I have lived in
or spent time has one or two traffic lights famous

(41:03):
for being just a pain in the key star. And
there was one UM which was right by, right right
across from a walmart. And this was years and years ago.
I have been passing through town Scott and it was
very late and it was about three in the morning.
I had just I have been doing like a concert

(41:23):
thing and three in the morning and heading home just
trying to get to the interstate. I'm waiting at this
UM normally a very large intersection, but because it was
three in the morning, and this is a relatively smaller
area it was. It was abandoned, and and so I
sat there what like eight ten minutes. I started thinking

(41:44):
about like society and stuff and how brainwashed I am
that I'm sitting here in an empty road for a
red light. A police officer drives by and like flashes
his lights real quick, and then, you know, I think, well, great,
this night did get where so it's surprised, and uh,
I'm like, well, I guess it should pull over something.
But he rolls his window down. He's just like, don't

(42:07):
pay attention to this light. Just go. It's just it's
gonna be red all night. No kid. It was like,
how long have you been here? Yeah? Yeah, you know,
I think most cities, like you said, most cities have
that one or two lights that has a bad reputation
like that. I mean that you know, is is timed
way too long one way and way too short the
other way when it should be the opposite. And this
this officer was like he was clearly this was not

(42:29):
the first time he told us about but he was
clearly pretty amused because I didn't tell him how long
I have been there. That's funny, you know that it
works that way. But you know, I've also noticed that
there's one close to my house, the one prior to
the one I'm talking about, you know, the one I
approached just before that you're going through that. Um, yeah,
I guess so, I mean, but but I understand that.
You know, like the main road, the main stretch that

(42:52):
that it covers is the road that typically has more traffic,
So it's always green on that side when I approach.
But I'll tell you it's really good that when I
approached and I do stop there and I'm the only
car around, you know that like the other side of
the road there's a park and i'm you know, behind
me as a school, and you know, there's times when
it's very busy, but at the time I'm going home,
it's not very busy at all. And I usually I

(43:12):
would think, well, I'm gonna be stuck here, but as
soon as I pull up it it changes almost immediately
for me. So it's a it's a really good system.
The cameras are aimed right, or the inductive loop or
whatever is working correctly, and it's nice when that happens.
But you're right, there's sometimes when that does not happen.
How about this, here's another little situation that could be maddening.
Let's say that, well, we were pretty uh, we're pretty

(43:33):
lucky here I think in Atlanta and that and and
maybe you haven't even recognized this, I don't know, but
when the lights change here in Atlanta, almost every single intersection,
I mean, with very few exceptions, the left hand you know,
the protected left hand turn always goes first. Oh yeah,
you know. Like so it may be that, you know,
the the through traffic gets a green and you get

(43:55):
the green signal to go as well, but more often
than not, it's just the protected left goes first, then
you know, the h and then the arrest of the
traffic is allowed to go. And it's almost always that way.
So you know exactly what to expect when light changes
that you know, okay, the left people are gonna go
first than me. And in other cities it's not like that.
What's it like, It's it's just everything. I mean, you know,

(44:17):
you could either be the left turn goes first, or
it could be that, you know, the through traffic goes first,
or um, you know, there any other situation, but it's
that there's no consistency to it. And I think that,
you know, once you're kind of spoiled to something like that,
you don't realize it until you traveled to another city,
and then it's like, what's going on with the lights here?
It's so it's so different, it's so unusual. Yeah, it's
something you just don't typically think of until you've experienced

(44:40):
something like what we have here in Atlanta. You know what,
Maybe you're right, Maybe I've gone soft on my on
my traffic light. Maybe. So it looks like we're getting
closer time, and it's it's time for one of our
one of the most bitter sweet things we do on
every episode of Car Stuff, Scott. We each have to
pick one more thing one Okay, I'll trick. I'll try

(45:05):
to pick one more thing out of my huge list here.
And we are not getting to even half of my notes.
I can tell you that. Yeah, I've got I've got
a bunch of stuff up here too. Um, and I
don't I don't know how we're gonna do it. Um,
do you want to go first? You want me to go?
Tell you what? I'll go first and you can wrap
up the whole thing. How about that? All right? Are
you sure. I'm positive? Okay, So let's let's talk about
light timing in particular yellow light timing, because this is

(45:27):
a source subject for a lot of people. This is
a huge source subject. Okay, all right, I just have
to say in defense of everybody who's gotten a ticket
for running quote unquote running a red light, and I'm
right there with you, guys, Uh, it's not always the case.
A lot of that is a lot of that is uh,

(45:47):
the issuing officers discretion and traffic at least yellow light
timing on traffic lights is by no means standardized nor
created equal. And you and I Scott stumbled upon um
possible unethical behavior when we were looking into our red
light camera podcast. Yes we did, Yeah, we did exactly right.

(46:11):
And what they're supposed to do is they're supposed to
add a second for you know, if there is a um,
if there is a red light camera, you're supposed to
add one second of yellow And many of the cases
they were reducing, you know, reducing it by a second,
taking way a second or even two seconds. So here's
the way it's supposed to be. They're supposed to be
sort of a standard, but it's not exactly a standard um,

(46:33):
four or five seconds for a typically yellow light is
is what you can expect here in the United States.
I mean that's that's typical, but three seconds is possible.
That's kind of the federal allowed minimum is three seconds. Now,
the way that it works here in Georgia is that
the yellow light must be lit for exactly one second
for every ten miles per hour or sixteen kilometers per

(46:55):
hour of posted speed limit on that road. So you
can calculate how long that yellow it is supposed to
last based on the speed limit for that road. And
I don't know if that really works out all the time.
I mean I've seen some that are you know, seem
to be way too short. Um. And again I mentioned that,
you know, if there's an intersection with a red light
camera in operation, if they're supposed to add one second

(47:16):
of yellow for that, you know, for that particular intersection
on top of the you know, the one second for
every ten miles per hour posted. Now in Colorado Springs, Colorado, uh,
they found that some of these lights, some of these
yellow lights have been time to just two seconds. I
can imagine a two second yellow light. That's not enough
time to get through some of these bigger intersections and

(47:37):
the you know, the federal safety minimum requires at least
three seconds, and that's again that's a that's there's there
for a reason that there's a there's a reason three
seconds is the minimum. I mean for the bigger intersections.
It takes that long sometimes where to register for you
to be able to clear the intersection safely before the
next green cycle appears. And I also I also think
that three seconds itself is too short because is Although

(48:02):
you will hear that Atlanta traffic is bad, and that
is correct. Um, there are some there are some clear
just um head count issues, number of car issues. Although
that's true, the people generally are not, you know, jerk drivers.
We don't have that mean reputation that some other cities have.

(48:23):
Sure not naming names, but listeners feel free to write
in if you've got some picks. The uh. The The
interesting thing though, is that even in a place where
people tend to be polite drivers, everybody in a city,
any city, is going to push that yellow light. Yeah,

(48:44):
and you know, one one little fail safe I guess
I don't know if it's even a failing and I
guess it would be for the police officers a fail safe.
They have something called confirmation lights at some intersections, and
so that means that the officer that's watching that intersection,
you know, like they're watching for a red light runner.
It's not a camera system, but they're they're watching that intersection.
They can see by a white light that lights up there.

(49:05):
I think it's above or below the signal. It's a
it's a small white light. So it's not confusing that
any drivers or anything, but it will indicate if a
car or a vehicle is in the intersection when the
light changed to red, so that if they're a distance
away and they don't have to be within you know,
the the sight line of the red light to be
able to see that the light was still red when
they were not quite through the intersection. They can spot

(49:27):
it from you know, like maybe the the the parking
lot that's kitty corner to that intersection, and they can
you know, then pull somebody over. So that's that's another
little law enforcement trick that you might want to watch
out for. I guess it's not really a trick. It's
just more of a way for them to be able
to monitor that section, um, you know, from a distance, yeah,
And ultimately I'm gonna say there's nothing wrong with it

(49:48):
because again, uh, following traffic lights does matter. It's what
keeps society together. Ben, It's it really does. And otherwise,
you know, it's the old thing that cats living with dog,
you know, the whole thing, right, Yeah, traffic lights are
you saying? Traffic lights, you know, are the staple on
the comic book that society. Let me put it this way,
all right, we all understand that, you know, when that

(50:09):
red lights there, we stop our four thousand pound machine
at a at a painted line on the road, and
we allow, we allow other four thousand pound machines or
more to cross through that intersection where we would have
been obliterated had we just decided to ignore that red light. Right,
So this is a strange thing, right, I mean, we
and and there are other things like this, And I
think about too, Like we're on a two lane road

(50:30):
and there's a yellow line painted down the middle, you
know where you're not supposed to cross that line. I
think about that too. How how fragile that that line is?
Like how what are I'm sorry I'm interrupting, but this
is such a big thing, Like what what are people
going to think four dred years in the future when
someone explains high speed traffic to them, and then you, well,
probably won't be high speed then. But and then you say, like, well,

(50:51):
why didn't you guys hit each other and say, well,
I mean, we hit each other all the time, but
we had this honor system of these painted lines. You
don't cross that painted line. I mean, I mean now,
I mean, but it seems funny when you think about
it like that. I mean, there's and I know there's
different ways to think about this thing, but but we
all just kind of uh, well at this point and
I'll say mindlessly, but we we we mindlessly obey these

(51:14):
these red, green, yellow lights. But it's a good thing
that we do. And you know, yeah, it's a very
it's a very good thing. And the here's my one
more thing. The story of traffic lights continues, and a
lot of the technology that we have seen slowly filtering
its way into into other parts of the world is
coming to your local traffic light. Ladies and gentlemen, uh

(51:37):
smart traffic lights right are are these? Here's this idea
that the traffic lights at the next intersections in your
town might be able to do something kind of like
artificial intelligence be able to communicate to each other with
a little bit more I guess sophistication. Uh the way,

(51:58):
so the lights are communicating with other lights instead of
the one central computer controlling what happens between this one
and that one. Yeah. So the the idea is that, um,
there are these professors and students at Carnegie Mellon University
who've got a pilot project going on in Pennsylvania now
in Pittsburgh, and the idea is that if they have

(52:19):
what they call a dynamic control system where these lights
can talk to each other. BMW and siemens are helping
develop this, by the way, um, then they will be
able to reduce the time that people spend in traffic
and and reduce emissions. But as a selfish person, let
me just point out that I put the most important
one first in that list. Um. So, so it is

(52:42):
it is possible that very soon traffic light games are
going to change entirely. And if you have a smartphone,
you can also check to find some apps that claim
to reduce the time you will spend in traffic. I
don't know about well. They like they claim to help
you beat red lights, red lights. Yeah, but but there,

(53:05):
you know, there's some other things like we had we
had mentioned some of those um absolute that will help
you drive, like ways or GPS stuff, and that's that's
a whole different story. But guys, I think we have
to get out of here for today. Isn't this crazy?
I mean, this is a shame, all right. So it's
fifty Well we're about fifty eight or fifty nine minutes

(53:25):
into this thing something to an hour, right, I really
have touched maybe a third of my notes. I was
gonna say maybe thirty two. Yeah, very specific. Then yeah,
it's it's uh, it's a shame that we're not gonna
be able to get all this out there. I mean,
maybe we should do a second part. Maybe maybe I
don't know how about not right now, let's let's regroup

(53:47):
because mine are scattered all over the place now because
we just started to pick and choose things. But but yeah,
there's a lot more here. We didn't even get to
talk about how accidents sometimes go up when a light
is installed. Uh. We didn't get to talk about urgency
vehicles and how they can control lights and fascinating stuff.
By the way, I had no idea until I read this.
I mean it's really unusual. Um, we didn't talk about

(54:09):
you talk about light lens sizes. No, we didn't talk
about the standards because they're going a strange direction in
the UK. Um. Uh. You know, we didn't talk about
how like the three methods of operation. We didn't There's
a lot of stuff. I mean, I know it gets,
you know, kind of down into the weeds, and maybe
some of it's a little bit boring, but hopefully we've

(54:30):
kept your attention along the way and and maybe you'll
take this opportunity to investigate just a little bit further,
you know, something that you found interesting here, because there's
plenty of interesting stuff and you wouldn't guess that on
the surface, but there really is if you dig just
a little deeper. And this is the way with so
many of our topics, if you go just a little
bit deeper, there's there's so much out there. You would
be astounded, you know, just how much information is out

(54:53):
there about the simple traffic light. Yeah, and you can
also in the meantime check out our or website car
Stuff Show dot com, where you can find all the
podcasts we've ever done, including a recent one we did
on road signs, which has a lot in common with
some of the stuff about traffic lights. Yeah, and then
there we did on one that was also called can
your Car Tell You when the Life's About to Change?

(55:14):
And that was that was focused on that outie system.
So there's another whole angle to this whole thing. There's
a there's just so much then yet, so we're gonna
head out. You should you should check this out if
you get a chance, and uh follow Scott and I
on Facebook and Twitter. Where're your Car stuff hs W
If you have some ideas, if you are a traffic
engineer with some tips for the average driver, then uh,

(55:37):
you know, or if you just if you have a
bad light in your neighborhood, in your neck of the
woods and you want to tell us about it, then
we'd love to hear from you. You can write to
us directly at car stuff and how stuff work dot com.
For more on this and thousands of other topics is
how stuff works dot com. Let us know what you think,
send an email to podcast at how stuff works dot com.

(56:00):
A completer