# Traffic Light Signal Different Loop Sequences around World

For smooth flow of traffic on roads, there are Traffic Signals and two standards are followed across the world for traffic lights loop sequence. Both are explained in this article:

# Loop Sequence (USA Style)

A USA style light comprises of a green (go ahead), amber (go ahead with a caution) and red (stop) light, respectively. This sequence can be only applied to one street, the other intersections will be different.

For example there are two streets: one has a lot of traffic and the other one is the exact opposite of it. Both will have different time intervals for the lights switch on and off. We can set the timings based on the traffic flow. Assume that for the busy street, green light is on for 12 seconds and 4 seconds, for busy and idle street, respectively. Amber light time interval remains constant for both the streets.

It is important to understand these time schedules so that the coding can be done likewise. While one street’s traffic will be stopped the other one will move. It is common sense, otherwise accidents will occur. Other factors like speed limit, street size, etc. influence the timings and flow. The situation can be stabilized by setting red lights in place for some seconds at the same time for both the streets, so that the drivers can make sense of the traffic lights flow.

# Loop Sequence (UK Style)

There is a very minute difference between the UK and USA style lights and it’s just a difference of a sequence. It prepares and alerts the drivers even more.

So, the UK style lights constitute of green (go ahead), amber (go ahead with a caution), red (stop), and red/amber (green light soon).

Hence, there is just an additional step before the green light turns on. All of this will be incorporated in the Arduino code (in main article) and it’d be possible for you to switch from one style to another by just altering a constant.

This is part of project article “Traffic Light Simulation using Arduino”