Positive - they keep traffic moving.Negative - they are always red when you approach them
Prepare to stop
Anyone driving a vehicle or riding a bicycle should obey a traffic light.
.... as a stop sign.
If there is a traffic light.
It should be treated as a stop sign.
A yellow arrow traffic light means that you should yield in the direction you are going. These are often in place when you are turning left.
When you see flashing red lights at a 4-way stop Light instead of normal traffic signals you should approach the intersection as if it was a 4-way stop sign, alternating N/S and E/W lanes proceeding through the intersection, one car at a time. Typically this type of situation happens when the traffic signal system is malfunctioning.
look both ways carefully.
You must STOP, and wait until GREEN then GO.
The opposite would be "light traffic".
Amber (or red) in a traffic light sequence means "stop," put the brakes on! Green means "go;" and yellow signifies that the traffic light is about to turn red (or amber), so you should start to slow down and prepare to stop.