So maybe someone can tell me who decided red means stop and so on?

Question

So who came up with that for train and traffic lights .. red means stop ... yellow means slow down .. and green means go?

Answer 1

Department of Transportation?

Answer 2

It wasn't always so on the railroads.

The signal systems evolved over time and railroads used their own systems until they were finally standardized.  The Union Signal Company makes the lions' share of signals that have been and are currently being used.

The first automatic signals were of the 'semaphore' type and did not displayits indications via a color (aspect), but rather conveyed information by changing the position of one or more 'blades' mounted atop the signal mast.  Later semaphore signals did display colored lights in conjunction with the blade's position.  These blades had three positions within a 90 degree arc.  Horizontal was stop (red), 45 degrees meant slow (yellow) and perpendicular meant clear (green).  If the movement of the blades through the arc was between horizontal and perpendicular in an upward direction, this was an 'upper quadrant' semaphore, or in the downward direction, a 'lower quadrant' semaphore.

Prior to that time, colored flags were displayed to carry information to the train crews.  But, quite the opposite of today, if the approaching train saw two green flags by day, or two green lights at night, it indicated that the train had orders waiting and must be stopped.  Red flags and lights meant proceed, no additional orders.

Flags today are used in conjunction with track bulletins when there are temporary speed restrictions, utilizing a yellow flag when approaching and a green flag at the end of the resrtiction, or maintenance of way working, which uses a red/yellow flag for an approaching train, a red flag that must not be passed until authorized to do so, and a green flag at the end of the limits of the restriction.

There are still a few semaphore signals here and there, but most today are either purely electrically controlled lighting different colored lights or multiple lights used together to form a 'line' of lights either upwards, (proceed) a 45 degree angle, (slow) or horizontal, (stop), or an electro-mechanical version, were there is actually moving lenses within the signal apparatus.

Why red for stop?  Why is a matador's cape red, when bulls are color blind?  Just the luck of the draw, I think.........

Answer 3

In 1868 British railroad signal engineer J P Knight invented the first traffic light, a lantern with red and green signals.

Answer 4

Ok... I dont know exactly WHO came up with it but heres some of what I found.. go to the links and read the rest for more in depth info on it all...

"First, the colors used by early railway signals were determined by what kinds of colored glass were available and because they had to work with the colored flame of an oil lamp. Early signals generally used red lights or white lights (i.e. clear glass) if the signal was to be just lit or unlit, and once it was realized that it was better to have a light all the time and just substitute a different color, the earliest code was red for stop/danger and white for clear. When it was realized that an intermediate color was needed for caution, green was used, as it was the only other suitable color available -- and I would think this last fact would also account for the use the same two colors in shipping, with aircraft then copying that.

Later as other lights became more common, white had to be replaced in railway signaling, so a suitable yellow glass was developed and introduced as the new caution color, green becoming the clear signal. These colors were then copied for traffic lights."

Also, studies conducted nearly 100 years ago that found bright red to be the first color that registers on our retinal nerve endings. Therefore, for people without color blindness, bright red catches the eye fastest--hence its traditional use as the universal color for fire, safety, danger, and perhaps traffic lights.

Hope this helps clear it up.

Answer 5

Yellow means more than slow down on the rails.  Most commonly, it means approach.  This means you slow your train down to a proscribed speed, say 20 mph, and prepare to stop short of the next signal.  You get one to get you prepared to stop because the next signal is probably red.  In some areas you can get a white signal.  This color is called lunar and it means to slow to restricted speed.  This means (loosely defined) going slow enough to stop within half the distance of a red signal or track obstruction.