I am trying to set this up using a Mitsubishi FX1S PLC and using the programme GX Developer. Can someone help construct the logic. "The traffic flow at the crossroad system is controlled using traffic lights which follow a standard UK sequence and also have an incorporated pedestrian crossing function. The sequence commences with both red lights and then continues with the standard sequence from N to S whilst E to W remains at the red state. Intervals of 2 seconds when the amber light is being utilised individually or in combination and 4 seconds when the green light is illuminated are required. When the N to S sequence has completed there is a 2 second delay with both red lights illuminated and then the E to W sequence is commenced and then standard operation is continued with the same time intervals. If either pedestrian crossing button are pressed the sequence will stay in the same pattern but there will be an extended delay when both red lights are illuminated simultaneously, this delay will be of 8s duration."

 

I designed on by using a microcontroller. I wrote it for American and European patterns. I don't think that listing it would help as it is in Parallax Propeller Assembler language. If you request, I will post it. There is a host of Adruino users here that might have a program.

 

I use the Mitsubishi FX series and have found the book by John Ridley " Mitsubishi FX Programmable Logic Controllers" (Newnes pub) very helpful. in the past.
It has various basic project examples, one being a simple traffic light controller that maybe expanded on.
The one I quoted is a little more $$
https://www.abebooks.com/servlet/SearchResults?sts=t&an=john+ridley&tn=Mitsubishi&kn=&isbn=
Max.
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Presumably you know the sequence of UK traffic lights.
First thing to do here is to draw a diagram of how this system will operate. Work out and draw the steps the system will go through. If you do this carefully, you will arrive at a "state chart". The system will eventually rotate back to the starting state.

In GX Developer I advise you to create your program using SFC - which is a kind of state machine approach. Each state block will be a certain fixed setting of all the lights on the junction. The SFC transitions from one state to the next depending either on time (a timer time-out contact) or on an input event - for example a pedestrian crossing button pressed.

For example: when the pedestrian button is pressed, the system transitions to a new state - the lights don't immediately change (so each state has the same lights) but a timer is started.

See the attached for some instructions. This is an excerpt from the complete programming manual - you can find the complete manual on line.