There is no exact time simply because no 2 intersections are the same, there are factors that change this time such as: How much traffic goes through the intersection on one direction?
A green light usually last a minute to two minutes.
When the traffic light comes into view and it's green, it was likely green for a long time, unless you also observe cars just starting to get going. If you see the traffic light is green in the distance we call this green light "stale", meaning it could turn yellow any second. A traffic light that just turned green, we call this green light "fresh", meaning it just turned green and it won't be turning yellow for a little while. Of course these times between from when it turns green then back to yellow and red again varies on the intersection. To answer the question when you're approaching a green traffic light you should prepare to stop as that green light is "stale". You don't necessarily have to slow down just get ready to hit the brake.
Stale green light is a term used in traffic terminology. Essentially, it means that the green light has been green so long that it's about to turn yellow.
It takes 2-3 minutes for a traffic light to change from green to red! (P.S I have counted the seconds myself!)
If you are blocking traffic flow for a long time then yes.
You can get a DOT card if you're color blind as long as you can distinguish between the red, amber, and green of a typical traffic light.
There is no exact time simply because no 2 intersections are the same, there are factors that change this time such as: How much traffic goes through the intersection on one direction?
A light
There is no specific length of time for a red light. Traffic engineers make that determination according to the flow of traffic.
As long as it's programmed to remain red. Those times are determined by the agency tasked with traffic management, and they'll decide that based on the width of the road being crossed, anticipated traffic patterns, etc.
about 3hours, if traffic is light
This differs depending on the intersection. Some intersections are forever flashing red. Some intersections only turn green when there is a trigger such as a pressure-pad or a crossing signal.