h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Two questions:

1. In Japan, why do they insist that the "go" light is blue instead of green, when it's the exact same color as the ones here in the states? Is Japan the odd man out, or do other countries have "blue" lights as well?

2. In the UK, why do some traffic lights flash yellow before going from red to green? Does this really help anything?

Ok, well three..

3. Is there any reason other than historic precedence why the red light is on top?

The only traffic lights in the UK that flash yellow (we call it 'amber' over here) are on pedestrian crossings. I don't know how things work in the States (although I have seen pictures of the 'WALK / DONT WALK' signs), but on our pedestrian crossings we have:

1) A red standing man to indicate 'Don't cross'
2) A green walking man to indicate 'Cross'
3) A flashing green man to indicate 'Get off the crossing 'cos the lights are about to change', which pedestrians usually take to mean 'Now's the time for that last minute sprint across the crossing'.

While the green man is flashing, the amber light flashes. This tells the traffic that it is OK to proceed if there is no one on the crossing. However, see last half of item (3) above.

As for the reason for the red light being on top, I understand that traffic lights were invented / first used in the States (Detroit 1919), so if you want to know why they are the way they are, try your local library. Or maybe there's a web site!

I have a question about traffic lights, too.

The stop-to-go sequence runs RED, RED & AMBER, GREEN.
The go-to-stop sequence runs GREEN, AMBER, RED.

Why no GREEN & AMBER?

Red = stop; Amber = notice of impending change of state; Green = go.

Green - Amber - Red

Red - Red & Amber - Green

Red&Amber is to inform approaching drivers that the lights are changing to green, rather than changing to red.

Given that the two fundamental states are red and green, and that amber exists solely to phase the transition so we don't have to stop dead with no notice, the four states ( red / red+amber / green /amber ) are sufficient.

OK, I can see the pure mathematical logic of it - we only NEED four combinations, yes. But why not make that fourth combination GREEN & AMBER instead of AMBER ALONE. That would be logical in a human way.

Then...GREEN & AMBER more patently means "This is changing to red", in the same way that RED & AMBER means "This is changing to green."

Having said that, you are highly unlikely to arrive at traffic lights on amber not having seen what the previous colour was. If they're about to change to red, you'll have seen them go from GREEN to AMBER, the amber phase being very short, and vice versa.

So they really only NEED, in practical terms, THREE phases - RED ALONE, AMBER ALONE, GREEN ALONE.

And now I've just come to thinking... Do we really need AMBER at all. Couldn't the RED and GREEN just flash to signify they are about to change?

Thanks for the interest, anyway!

I would think Green+Amber isn't used instead of just Amber, because if a driver were to 'miss seeing' the Amber light for any reason, and just see the Green, he/she may continue to drive, whilst the lights were changing (Which could also mean him/her jumping a red light by a few seconds).

It's a minor niggle-type-thing I know, but I assume it's something governments have to consider when making the traffic rules; they would rather people knew when to stop.

Excellent point, and probably correct. That's almost put my mind at rest on the matter. Thanks.

Exactly right.

I believe the amber was added in America. A policeman came up with the idea (I think) after seeing the number of accidents that were caused by the lights changing straight from green to red and back again. Green - amber - red - amber - green wouldn't be a good idea because drivers wouldn't know what the next colour would be when the lights showed amber. Something is needed to differentiate between 'about to go red' and 'about to go green'. I don't think it matters much what the sequence is as long as everybody is familiar with it, so we'll probably stick with the existing sequence forever.

As far as blue & green goes, some cultures make no distinction between the two colours (green after all is blue with a bit of yellow). I have no idea if this is the case in Japan.

A big misconception is that Green means "Go", when it really means "Get ready to go after checking the way is clear." This is because of another misconception about the Amber light. Amber is supposed to mean "Get ready to stop". Most people, however, believe it means "Go really, really fast so I can save myself two minutes".

Because of people like this, the Green light should not be seen as the point at which to plant their foot.

Don´t know if I am right, but isn´t there a green-amber sequence in Italy ?

Well, just thinking about my last trip to italy. When ?
This century ? Hmmmm.
*walking downstairs to stray cats café*
*thinking*
*enjoyingespresso*
*still thinking*

Okay.. Here in the states it works this way:

Stop to go.. Red.. Green. (no amber)

Go to stop: Green .. Green & amber ... Red

According to the teaching manuals, amber is defined as,
"Stop and allow the intersection to clear" ... However, in actualitiy it works much like has been described re the walk/don't walk signs... it's interpretted as "Hit the accelerator and get through the light before it turns!" This has given rise to the following Trucker's Joke (Short version):

Two guys are traveling through a town. They come to a traffic light which is turning red... Driver barrels through just as the red appears.

Passenger: Why did you do that?
Driver: My buddy does it.

Scene repeats several times.

They come to a light which is red, but on approach turns green. Driver slams on his brakes.

Passenger: Why did you do -that-?? It's -green- for pete's sake!
Driver: My buddy may be coming the other way.

I live in Italy right now, and the sequence is;

Green - Amber - Red for stopping

and Red - Green for going..

No mixed colours whatsoever. Italians are all awful drivers anyway . Infact in the south, especially in cities, some drivers ignore the lights altogether, ie, if the way is clear, even if it's on red, they go.

Would mean a great progress for mankind, i think. Neglecting traffic lights.
Here in Germany, it´s quite expensive, I think.
And -btw- I know a researcher whose driving lessons would becalm in case of switching them off.

I know this has been said many times before in many other places, but it may as well be said here...

We must all have noticed how much more smoothly the traffic flows at cross-junctions when the traffic lights aren't working and it's left to everyone's common sense, i.e. no major build-ups on any of the approaches.

However, I'm sure this is due to people's caution because it is an out-of-the-ordinary scenario. Were this always the set-up, i.e. no traffic lights, drivers would go crazy and show no consideration for others.

PS: While I'm on, may I introduce another strand?

How annoyed do you get at cyclists who insist on using the roads but ignoring the traffic lights? JUST HOW ANNOYED?@#$! IS THERE NOTHING LOUDER ON THIS KEYBOARD THAN CAPS? I DON'T KNOW HOW TO DO BOLD ITALIC - AAARRRGH!!!

I've just noticed how bad that looks... "cyclists who insist on using the roads"... as if they shouldn't. I don't have a problem with cyclists using the roads, but if they do they must obey all the rules. There.

No, cyclists should be lined up and shot at dawn, I have never met a nice cyclist.

The first time I encountered a driver who ignored traffic lights was on pretty much my first driving lesson. The situation was this. In Bangor, Wales, there are traffic lights at a T-junction at the top of a hill. I was heading up the hill towards the T-junction and the lights were green for the traffic on my road. The road from the right had a filter for traffic turning left, which was green, while the other light for traffic going straight on was red. (Are you with me so far!)

As I approached the junction and started to turn right, some STUPID WOMAN went straight through the red light on the right. The driving instructor and I both went for the brake at almost the same time. If we hadn't, she'd have hit the car! From the look she gave us, she hadn't a clue that she'd done anything wrong!

Yellow (as here in the states we call it) is supposed to mean "If you can make a safe stop, then stop. If not, go." Normally it just means "Speed up to get through unless you will enter the intersection after it turns red (Legal In Legal Out)." Why do they have the red/flashing yellow anyways (It isn't that way here -- Red-yellow-green-red-etc), you can't start to drive until it turns green anyways and if you really need to know when it will change, watch the lights from the other direction.