Traffic Light Management for Municipal

PROGRAM TRAFFIC_LIGHT_INTERSECTION_CONTROL
VAR
    // Inputs
    ped_button_ns : BOOL;      // North-South pedestrian request
    ped_button_ew : BOOL;      // East-West pedestrian request
    vehicle_detect_ns : BOOL;
    vehicle_detect_ew : BOOL;

    // Outputs
    light_ns_red : BOOL;
    light_ns_yellow : BOOL;
    light_ns_green : BOOL;
    light_ew_red : BOOL;
    light_ew_yellow : BOOL;
    light_ew_green : BOOL;
    ped_walk_ns : BOOL;
    ped_walk_ew : BOOL;

    // State Machine
    phase : INT := 0;  // 0=NS Green, 1=NS Yellow, 2=EW Green, 3=EW Yellow
    timer : INT := 0;

    // Timing Constants (in 100ms cycles)
    GREEN_MIN : INT := 200;    // 20 seconds minimum
    GREEN_MAX : INT := 600;    // 60 seconds maximum
    YELLOW_TIME : INT := 30;   // 3 seconds
    RED_CLEAR : INT := 20;     // 2 seconds all-red


    // Infrastructure Monitoring
    Distribution_Pressure : REAL;
    Reservoir_Level : REAL;
    Pump_Station_Status : ARRAY[1..5] OF BOOL;

    // Remote Monitoring
    RTU_Communication : ARRAY[1..10] OF BOOL;  // Remote Terminal Units
    Telemetry_Update_Rate : TIME := T#30s;
    SCADA_Alarms : INT;

    // Emergency Response
    Boil_Water_Advisory : BOOL;
    Water_Main_Break : BOOL;
    Emergency_Mode : BOOL;
END_VAR

// ==========================================
// BASE APPLICATION LOGIC
// ==========================================

timer := timer + 1;

CASE phase OF
    0: // North-South Green
        light_ns_green := TRUE;
        light_ns_yellow := FALSE;
        light_ns_red := FALSE;
        light_ew_red := TRUE;
        ped_walk_ns := (timer > 50);  // Delayed walk signal

        IF timer > GREEN_MAX OR
           (timer > GREEN_MIN AND vehicle_detect_ew AND NOT vehicle_detect_ns) THEN
            phase := 1;
            timer := 0;
        END_IF;

    1: // North-South Yellow
        light_ns_yellow := TRUE;
        light_ns_green := FALSE;
        ped_walk_ns := FALSE;

        IF timer > YELLOW_TIME THEN
            phase := 2;
            timer := 0;
            light_ns_red := TRUE;
        END_IF;

    2: // East-West Green
        light_ew_green := TRUE;
        light_ew_yellow := FALSE;
        light_ew_red := FALSE;
        light_ns_red := TRUE;
        ped_walk_ew := (timer > 50);

        IF timer > GREEN_MAX OR
           (timer > GREEN_MIN AND vehicle_detect_ns AND NOT vehicle_detect_ew) THEN
            phase := 3;
            timer := 0;
        END_IF;

    3: // East-West Yellow
        light_ew_yellow := TRUE;
        light_ew_green := FALSE;
        ped_walk_ew := FALSE;

        IF timer > YELLOW_TIME THEN
            phase := 0;
            timer := 0;
            light_ew_red := TRUE;
        END_IF;
END_CASE;

// ==========================================
// MUNICIPAL SPECIFIC LOGIC
// ==========================================

    // Distribution System Monitoring
    IF Distribution_Pressure < Min_Distribution_Pressure THEN
        Low_Pressure_Alarm := TRUE;
        // Start backup pump
        Pump_Station_Status[Backup_Pump] := TRUE;
    END_IF;

    // SCADA Integration
    FOR i := 1 TO 10 DO
        IF NOT RTU_Communication[i] THEN
            SCADA_Alarms := SCADA_Alarms + 1;
            // Alert operator of communication loss
        END_IF;
    END_FOR;

    // Emergency Response
    IF Water_Main_Break THEN
        Emergency_Mode := TRUE;
        // Isolate affected zone
        Zone_Isolation_Valves := TRUE;
    END_IF;

// ==========================================
// MUNICIPAL SAFETY INTERLOCKS
// ==========================================

    Production_Allowed := NOT Emergency_Mode
                          AND NOT Boil_Water_Advisory
                          AND (Distribution_Pressure >= Min_Pressure);