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# Physics/Traffic Lights.

Question
Dear Prof Richard

http://en.wikipedia.org/wiki/Traffic_light
http://www.engineersgarage.com/electronic-circuits/traffic-light-signal-555
http://www.555-timer-circuits.com/traffic-lights.html
http://en.wikipedia.org/wiki/Seven-segment_display

In the typical sequence of color phases:

Green Light : Illumination of the green light allows traffic to proceed in the direction denoted, if it is safe to do so

Orange Light : Illumination of the orange/amber light denoting prepare to stop short of the intersection, if it is safe to do so

Red Light : Illumination of the red signal prohibits any traffic from proceeding

Query
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Can a Single 7 Segment LED Display be used as an alternative
to the above three traffic lights with modifications in the control circuit ?

i.e.

0 Indicates Stop -> Similar to Red Light.
1 Indicates Stop Short Of -> Similar to Orange Light.
2 Indicates Proceed -> Similar to Green Light.

i.e. Instead of three light signals (three LED for each color red,orange and green) use of
a Single 7 Segment LED Display (indicates Number instead of colors) as source of Traffic Lights.

What are the Pros and Cons if this can be achieved ?

Do you feel showing Human Being Symbols (Red and Green Color)
would be a Bottleneck in the Single 7 Segment LED Display ?

In that Case Number 8 for Human Being Walk Stop Symbol and Number 9 for Human Being Walk Start Symbol can be used ?

The Single 7 Segment LED Color could be Blue or White with a Black
Background.

Note : The Circle Color Shape is replace with a Rectangle (7 Segment LED) Shape for this Traffic Light.

Thanks & Regards,
Prashant S Akerkar

That's an interesting concept, especially some people are colorblind.  Here in the US, red is at the top and green at the bottom so that people can tell the difference.  I'm sure there would be an energy savings if they just used LED colors without considering symbols.
Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment Dear Prof Richard Thank you. Thanks & Regards, Prashant S Akerkar

Physics

Volunteer

#### Richard J. Raridon

##### Expertise

I can answer most questions in undergraduate physics courses, including electricity and magnetism, atomic and nuclear, mechanics and optics.

##### Experience

I have taught undergraduate physics courses

Organizations
Sigma Xi, AAAS, SE section of APS

Education/Credentials
BA in math, MA in physics, PhD in physical chemistry

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Fellow of AAAS