How can I correct my m-file traffic simulation so that each of the eight traffic lights only becomes green or red based on the density count of cars at the two junctions?

clc;
clear;
% Parameters
laneWidth = 7;
roadWidth = 2 * laneWidth;
mainLength = 200;
junctionLength = 100;
leftOffset = 50;   
rightOffset = -50; 
roadColor = [0.2 0.2 0.2];
lineColor = [1 1 1];
carLength = 4;
carWidth = 2;
numCars = 6;
v_max = 0.2;        % Max speed
safeDistance = 6;   % Minimum distance between cars
acceleration = 0.01; % Speed change per step
spawnInterval = 200; 
stopDistance = 10;  % Distance at which cars check traffic light
% Lane-specific traffic light colors for each junction
leftTopLaneColor = [1 0 0];    % Red (initial for left junction, top lane)
leftBottomLaneColor = [0 1 0]; % Green (initial for left junction, bottom lane)
rightTopLaneColor = [1 0 0];   % Red (initial for right junction, top lane)
rightBottomLaneColor = [0 1 0];% Green (initial for right junction, bottom lane)
leftTopDiagLaneColor = [1 0 0];    % Red (initial for left junction, top lane)
leftBottomDiagLaneColor = [0 1 0]; % Green (initial for left junction, bottom lane)
rightTopDiagLaneColor = [1 0 0];   % Red (initial for right junction, top lane)
rightBottomDiagLaneColor = [0 1 0];% Green (initial for right junction, bottom lane)
% Frame counter for light updates
frameCount = 0;
updateInterval = 500; % Update lights every 500 frames (~5 seconds)
yellowDuration = 100; % frames for yellow light (~1 second)
lightPhase = 'normal'; % states: 'normal', 'yellowToRed', 'yellowToGreen'
yellowCounter = 0;     % counter for yellow phase
% Create figure
figure;
set(gcf, 'Color', [1 1 1]);
hold on;
axis equal;
axis off;
xlim([-mainLength/2-50 mainLength/2+50]);
ylim([-mainLength/2-50 mainLength/2+50]);
%% Plot static roads
x_main = [-mainLength/2, mainLength/2, mainLength/2, -mainLength/2];
y_main = [-roadWidth/2 -roadWidth/2 roadWidth/2 roadWidth/2];
fill(x_main, y_main, roadColor, 'EdgeColor', 'none');
x_leftVert = [-roadWidth/2 + leftOffset, roadWidth/2 + leftOffset, ...
    roadWidth/2 + leftOffset, -roadWidth/2 + leftOffset];
y_leftVert = [-junctionLength/2, -junctionLength/2, junctionLength/2, junctionLength/2];
fill(x_leftVert, y_leftVert, roadColor, 'EdgeColor', 'none');
x_rightVert = [-roadWidth/2 + rightOffset, roadWidth/2 + rightOffset, ...
    roadWidth/2 + rightOffset, -roadWidth/2 + rightOffset];
y_rightVert = [-junctionLength/2, -junctionLength/2, junctionLength/2, junctionLength/2];
fill(x_rightVert, y_rightVert, roadColor, 'EdgeColor', 'none');
x_dashes = linspace(-mainLength/2, mainLength/2, 50);
for i = 1:2:length(x_dashes)-1
    plot(x_dashes(i:i+1), [0 0], '--', 'Color', lineColor, 'LineWidth', 1.5);
end
y_dashes = linspace(-junctionLength/2, junctionLength/2, 10);
for i = 1:2:length(y_dashes)-1
    plot([leftOffset leftOffset], y_dashes(i:i+1), '--', 'Color', lineColor, 'LineWidth', 1.5);
    plot([rightOffset rightOffset], y_dashes(i:i+1), '--', 'Color', lineColor, 'LineWidth', 1.5);
end
%% Plot circles at junctions
circleRadius = 2;
junctionCircleLeft1 = rectangle('Position', [leftOffset-12 - circleRadius, -circleRadius-12, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', leftBottomLaneColor, 'EdgeColor', 'none'); % Bottom lane
junctionCircleLeft2 = rectangle('Position', [leftOffset+12 - circleRadius, -circleRadius+12, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', leftTopLaneColor, 'EdgeColor', 'none'); % Top lane
junctionCircleRight1 = rectangle('Position', [rightOffset-12 - circleRadius, -circleRadius-12, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', rightBottomLaneColor, 'EdgeColor', 'none'); % Bottom lane
junctionCircleRight2 = rectangle('Position', [rightOffset+12 - circleRadius, -circleRadius+12, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', rightTopLaneColor, 'EdgeColor', 'none'); % Top lane
%% Additional Traffic Lights (Diagonally Opposite, 0.5 unit outward)
offset = 0.5; % Distance away from the road
% Left Junction Additional Lights
junctionCircleLeft3 = rectangle('Position', [leftOffset+12 - circleRadius, -circleRadius-12-offset, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', leftBottomLaneColor, 'EdgeColor', 'none'); % Diagonal bottom opposite
junctionCircleLeft4 = rectangle('Position', [leftOffset-12 - circleRadius, -circleRadius+12+offset, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', leftTopLaneColor, 'EdgeColor', 'none'); % Diagonal top opposite
% Right Junction Additional Lights
junctionCircleRight3 = rectangle('Position', [rightOffset+12 - circleRadius, -circleRadius-12-offset, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', rightBottomLaneColor, 'EdgeColor', 'none'); % Diagonal bottom opposite
junctionCircleRight4 = rectangle('Position', [rightOffset-12 - circleRadius, -circleRadius+12+offset, 2*circleRadius, 2*circleRadius], ...
    'Curvature', [1 1], 'FaceColor', rightTopLaneColor, 'EdgeColor', 'none'); % Diagonal top opposite
%% Vehicle Count Texts
textLeftTop = text(leftOffset+22, 14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textLeftBottom = text(leftOffset-36, -14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textRightTop = text(rightOffset+22, 14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textRightBottom = text(rightOffset-36, -14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
% Additional Vehicle Count Texts for Diagonal Lights
textLeftTopDiag = text(leftOffset-36, 14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textLeftBottomDiag = text(leftOffset+22, -14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textRightTopDiag = text(rightOffset-36, 14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
textRightBottomDiag = text(rightOffset+22, -14, 'Vs: 0', 'FontSize', 6, 'Color', 'black', 'FontWeight', 'bold');
%% Initialize cars
carColors = lines(6); 
cars = struct([]);
carRects = gobjects(0);
% Initial car spawning in all directions
dirs = {'right', 'left', 'up', 'down'};
for d = 1:length(dirs)
    for i = 1:numCars
        switch dirs{d}
            case 'right'
                x = -mainLength/2 - (i-1)*spawnInterval;
                y = -laneWidth/2;
            case 'left'
                x = mainLength/2 + (i-1)*spawnInterval;
                y = laneWidth/2;
            case 'up'
                x = rightOffset + laneWidth/2;  % Move to right lane
                y = mainLength/2 - (i-1)*spawnInterval;
            case 'down'
                x = leftOffset - laneWidth/2;   % Move to left lane
                y = mainLength/2 + (i-1)*spawnInterval;
        end
        cars(end+1).x = x;
        cars(end).y = y;
        cars(end).dir = dirs{d};
        cars(end).v_current = v_max;
        cars(end).turn = randi([0 2]);
        cars(end).turned = false;
        cars(end).color = carColors(mod(i+10*d, size(carColors,1))+1,:);
        if strcmp(dirs{d}, 'up') || strcmp(dirs{d}, 'down')
            carRects(end+1,1) = rectangle('Position', [x - carWidth/2 y carWidth carLength], ...
                'FaceColor', cars(end).color, 'EdgeColor', 'none');
        else
            carRects(end+1,1) = rectangle('Position', [x y-carWidth/2 carLength carWidth], ...
                'FaceColor', cars(end).color, 'EdgeColor', 'none');
        end
    end
end
%% Animation loop
% Initialize (before the animation loop if not already declared)
leftJunctionLocked = false;
rightJunctionLocked = false;
while true
    % Update frame counter
    frameCount = frameCount + 1;
    % Count cars near each junction for top and bottom lanes
    leftTopCarCount = 0;
    leftBottomCarCount = 0;
    rightTopCarCount = 0;
    rightBottomCarCount = 0;
    leftTopDiagCarCount = 0;
    leftBottomDiagCarCount = 0;
    rightTopDiagCarCount = 0;
    rightBottomDiagCarCount = 0;
    densityRange = 30; % Increased from 20 to 30 to capture more cars
    for i = 1:length(cars)
        if ~cars(i).turned && cars(i).v_current < 0.01 % Count stopped cars only
            % Left junction (x=35)
            % Right-moving (bottom lane, y=-1.75): count cars in x=5 to 35
            % Left-moving (top lane, y=1.75): count cars in x=35 to 65
            if strcmp(cars(i).dir, 'right') && cars(i).x >= leftOffset-30 && cars(i).x <= leftOffset
                if cars(i).y == -laneWidth/2 % Bottom lane (y=-1.75)
                    leftBottomCarCount = leftBottomCarCount + 1;
                end
            elseif strcmp(cars(i).dir, 'left') && cars(i).x >= leftOffset && cars(i).x <= leftOffset+30
                if cars(i).y == laneWidth/2 % Top lane (y=1.75)
                    leftTopCarCount = leftTopCarCount + 1;
                end
            end
            % Right junction (x=-35)
            % Right-moving (bottom lane, y=-1.75): count cars in x=-65 to -35
            % Left-moving (top lane, y=1.75): count cars in x=-35 to -5
            if strcmp(cars(i).dir, 'right') && cars(i).x >= rightOffset-30 && cars(i).x <= rightOffset
                if cars(i).y == -laneWidth/2 % Bottom lane (y=-1.75)
                    rightBottomCarCount = rightBottomCarCount + 1;
                end
            elseif strcmp(cars(i).dir, 'left') && cars(i).x >= rightOffset && cars(i).x <= rightOffset+30
                if cars(i).y == laneWidth/2 % Top lane (y=1.75)
                    rightTopCarCount = rightTopCarCount + 1;
                end
            end
        end
    end
    % Update traffic lights based on density every updateInterval frames
    if strcmp(lightPhase, 'normal') && mod(frameCount, updateInterval) == 0
        % Switch to yellow phase before changing lights
        lightPhase = 'yellowToRed';
        yellowCounter = 0;
        % Save current states to know what’s transitioning
        prevLeftTop = leftTopLaneColor;
        prevLeftBottom = leftBottomLaneColor;
        prevRightTop = rightTopLaneColor;
        prevRightBottom = rightBottomLaneColor;
        prevLeftTopDiag = leftTopDiagLaneColor;
        prevLeftBottomDiag = leftBottomDiagLaneColor;
        prevRightTopDiag = rightTopDiagLaneColor;
        prevRightBottomDiag = rightBottomDiagLaneColor;
        % Set yellow wherever green exists
        if all(prevLeftTop == [0 1 0]), leftTopLaneColor = [1 1 0]; end
        if all(prevLeftBottom == [0 1 0]), leftBottomLaneColor = [1 1 0]; end
        if all(prevRightTop == [0 1 0]), rightTopLaneColor = [1 1 0]; end
        if all(prevRightBottom == [0 1 0]), rightBottomLaneColor = [1 1 0]; end
        if all(prevLeftTopDiag == [0 1 0]), leftTopDiagLaneColor = [1 1 0]; end
        if all(prevLeftBottomDiag == [0 1 0]), leftBottomDiagLaneColor = [1 1 0]; end
        if all(prevRightTopDiag == [0 1 0]), rightTopDiagLaneColor = [1 1 0]; end
        if all(prevRightBottomDiag == [0 1 0]), rightBottomDiagLaneColor = [1 1 0]; end
        % Update visuals
        junctionCircleLeft1.FaceColor = leftBottomLaneColor;
        junctionCircleLeft2.FaceColor = leftTopLaneColor;
        junctionCircleLeft3.FaceColor = leftBottomLaneColor;
        junctionCircleLeft4.FaceColor = leftTopLaneColor;
        junctionCircleRight1.FaceColor = rightBottomLaneColor;
        junctionCircleRight2.FaceColor = rightTopLaneColor;
        junctionCircleRight3.FaceColor = rightBottomLaneColor;
        junctionCircleRight4.FaceColor = rightTopLaneColor;
    elseif strcmp(lightPhase, 'yellowToRed')
        yellowCounter = yellowCounter + 1;
        if yellowCounter >= yellowDuration
            % After yellow, determine which lane gets green based on car count
            lightPhase = 'normal';
            % Example logic: Give green to the most congested lane at each junction
            % LEFT junction
            if leftTopCarCount > leftBottomCarCount
                leftTopLaneColor = [0 1 0];    % Green
                leftBottomLaneColor = [1 0 0]; % Red
            else
                leftTopLaneColor = [1 0 0];
                leftBottomLaneColor = [0 1 0];
            end
            % RIGHT junction
            if rightTopCarCount > rightBottomCarCount
                rightTopLaneColor = [0 1 0];    % Green
                rightBottomLaneColor = [1 0 0]; % Red
            else
                rightTopLaneColor = [1 0 0];
                rightBottomLaneColor = [0 1 0];
            end
            % Update visuals
            junctionCircleLeft1.FaceColor = leftBottomLaneColor;
            junctionCircleLeft2.FaceColor = leftTopLaneColor;
            junctionCircleLeft3.FaceColor = leftBottomLaneColor;
            junctionCircleLeft4.FaceColor = leftTopLaneColor;
            junctionCircleRight1.FaceColor = rightBottomLaneColor;
            junctionCircleRight2.FaceColor = rightTopLaneColor;
            junctionCircleRight3.FaceColor = rightBottomLaneColor;
            junctionCircleRight4.FaceColor = rightTopLaneColor;
        end
    end
    % Update vehicle count text
    set(textLeftTop, 'String', ['Vs: ' num2str(leftTopCarCount)]);
    set(textLeftBottom, 'String', ['Vs: ' num2str(leftBottomCarCount)]);
    set(textRightTop, 'String', ['Vs: ' num2str(rightTopCarCount)]);
    set(textRightBottom, 'String', ['Vs: ' num2str(rightBottomCarCount)]);
    % Update additional vehicle count text (same values, opposite side)
    set(textLeftTopDiag, 'String', ['Vs: ' num2str(leftTopCarCount)]);
    set(textLeftBottomDiag, 'String', ['Vs: ' num2str(leftBottomCarCount)]);
    set(textRightTopDiag, 'String', ['Vs: ' num2str(rightTopCarCount)]);
    set(textRightBottomDiag, 'String', ['Vs: ' num2str(rightBottomCarCount)]);
    for i = 1:length(cars)
        % Check for car ahead
        minDist = inf;
        for j = 1:length(cars)
            if i == j
                continue;
            end
            if strcmp(cars(i).dir, cars(j).dir)
                if strcmp(cars(i).dir, 'right')
                    if cars(j).x > cars(i).x
                        dist = cars(j).x - cars(i).x;
                        if dist < minDist
                            minDist = dist;
                        end
                    end
                elseif strcmp(cars(i).dir, 'left')
                    if cars(j).x < cars(i).x
                        dist = cars(i).x - cars(j).x;
                        if dist < minDist
                            minDist = dist;
                        end
                    end
                end
            end
        end
        % Check traffic light for cars approaching junctions
        stopAtJunction = false;
        if ~cars(i).turned
            if cars(i).turn == 1 && strcmp(cars(i).dir, 'right') && abs(cars(i).x - leftOffset) <= stopDistance
                if all(leftBottomLaneColor == [1 0 0]) % Red light for bottom lane at left junction
                    stopAtJunction = true;
                end
            elseif cars(i).turn == 1 && strcmp(cars(i).dir, 'left') && abs(cars(i).x - leftOffset) <= stopDistance
                if all(leftTopLaneColor == [1 0 0]) % Red light for top lane at left junction
                    stopAtJunction = true;
                end
            elseif cars(i).turn == 2 && strcmp(cars(i).dir, 'right') && abs(cars(i).x - rightOffset) <= stopDistance
                if all(rightBottomLaneColor == [1 0 0]) % Red light for bottom lane at right junction
                    stopAtJunction = true;
                end
            elseif cars(i).turn == 2 && strcmp(cars(i).dir, 'left') && abs(cars(i).x - rightOffset) <= stopDistance
                if all(rightTopLaneColor == [1 0 0]) % Red light for top lane at right junction
                    stopAtJunction = true;
                end
            end
        end
        % Gradual braking or acceleration
        if stopAtJunction
            cars(i).v_current = 0; % Stop at red light
        elseif minDist < safeDistance
            cars(i).v_current = max(0, cars(i).v_current - acceleration);
        elseif cars(i).v_current < v_max
            cars(i).v_current = min(v_max, cars(i).v_current + acceleration);
        end
        % Move car
        if strcmp(cars(i).dir, 'right')
            cars(i).x = cars(i).x + cars(i).v_current;
        elseif strcmp(cars(i).dir, 'left')
            cars(i).x = cars(i).x - cars(i).v_current;
        elseif strcmp(cars(i).dir, 'up')
            cars(i).y = cars(i).y + cars(i).v_current;
        elseif strcmp(cars(i).dir, 'down')
            cars(i).y = cars(i).y - cars(i).v_current;
        end
        % Release junction lock when car exits intersection area
        if leftJunctionLocked
            anyInLeft = false;
            for j = 1:length(cars)
                if abs(cars(j).x - leftOffset) < 2 && abs(cars(j).y) < 2
                    anyInLeft = true;
                    break;
                end
            end
            if ~anyInLeft
                leftJunctionLocked = false;
            end
        end
        if rightJunctionLocked
            anyInRight = false;
            for j = 1:length(cars)
                if abs(cars(j).x - rightOffset) < 2 && abs(cars(j).y) < 2
                    anyInRight = true;
                    break;
                end
            end
            if ~anyInRight
                rightJunctionLocked = false;
            end
        end
        % Turn if needed and adjust lane
        if ~cars(i).turned
            switch cars(i).dir
                case 'right'
                    % Turn left at LEFT junction
                    if cars(i).turn == 1 && abs(cars(i).x - leftOffset) < 1 && ~leftJunctionLocked
                        cars(i).dir = 'up';
                        cars(i).x = leftOffset + laneWidth/2; % Stay aligned in upward right lane
                        cars(i).y = -laneWidth/2;             % Bottom lane y-position
                        cars(i).turned = true;
                        leftJunctionLocked = true;           % Lock junction
                        % Turn right at RIGHT junction
                    elseif cars(i).turn == 2 && abs(cars(i).x - rightOffset) < 1 && ~rightJunctionLocked
                        cars(i).dir = 'down';
                        cars(i).x = rightOffset - laneWidth/2;
                        cars(i).y = -laneWidth/2;
                        cars(i).turned = true;
                        rightJunctionLocked = true;
                    end
                case 'left'
                    % Turn left at RIGHT junction
                    if cars(i).turn == 1 && abs(cars(i).x - rightOffset) < 1 && ~rightJunctionLocked
                        cars(i).dir = 'up';
                        cars(i).x = rightOffset + laneWidth/2;
                        cars(i).y = laneWidth/2;
                        cars(i).turned = true;
                        rightJunctionLocked = true;
                        % Turn right at LEFT junction
                    elseif cars(i).turn == 2 && abs(cars(i).x - leftOffset) < 1 && ~leftJunctionLocked
                        cars(i).dir = 'down';
                        cars(i).x = leftOffset - laneWidth/2;
                        cars(i).y = laneWidth/2;
                        cars(i).turned = true;
                        leftJunctionLocked = true;
                    end
            end
        end
        % Update rectangle
        if strcmp(cars(i).dir, 'up') || strcmp(cars(i).dir, 'down')
            set(carRects(i), 'Position', [cars(i).x - carWidth/2 cars(i).y carWidth carLength]);
        else
            set(carRects(i), 'Position', [cars(i).x cars(i).y-carWidth/2 carLength carWidth]);
        end
    end
    % Remove cars that go offscreen
    toRemove = [];
    for i = 1:length(cars)
        if abs(cars(i).x) > mainLength/2 + 50 || abs(cars(i).y) > mainLength/2 + 50
            delete(carRects(i));
            toRemove(end+1) = i;
        end
    end
    cars(toRemove) = [];
    carRects(toRemove) = [];
    % Random spawning in all directions
    if rand < 0.02
        % Right
        cars(end+1).x = -mainLength/2 - 10;
        cars(end).y = -laneWidth/2;
        cars(end).dir = 'right';
    elseif rand < 0.02
        % Left
        cars(end+1).x = mainLength/2 + 10;
        cars(end).y = laneWidth/2;
        cars(end).dir = 'left';
    elseif rand < 0.02
    elseif rand < 0.02
        % Up
        cars(end+1).x = rightOffset + laneWidth/2;  % Right lane
        cars(end).y = -mainLength/2 - 10;
        cars(end).dir = 'up';
    elseif rand < 0.02
        % Down
        cars(end+1).x = leftOffset - laneWidth/2;   % Left lane
        cars(end).y = mainLength/2 + 10;
        cars(end).dir = 'down';
    end
    if length(cars) > length(carRects)
        idx = length(cars);
        cars(idx).v_current = v_max;
        cars(idx).turn = randi([0 2]);
        cars(idx).turned = false;
        cars(idx).color = carColors(mod(randi(20), size(carColors,1))+1,:);
        if strcmp(cars(idx).dir, 'up') || strcmp(cars(idx).dir, 'down')
            carRects(idx,1) = rectangle('Position', [cars(idx).x - carWidth/2 cars(idx).y carWidth carLength], ...
                'FaceColor', cars(idx).color, 'EdgeColor', 'none');
        else
            carRects(idx,1) = rectangle('Position', [cars(idx).x cars(idx).y - carWidth/2 carLength carWidth], ...
                'FaceColor', cars(idx).color, 'EdgeColor', 'none');
        end
    end
    pause(0.01);
end

[BASHIR]

I need the corrected m-file code

[Torsten]

What a strange if-elseif construct ...

% Random spawning in all directions
    if rand < 0.02
        % Right
        cars(end+1).x = -mainLength/2 - 10;
        cars(end).y = -laneWidth/2;
        cars(end).dir = 'right';
    elseif rand < 0.02
        % Left
        cars(end+1).x = mainLength/2 + 10;
        cars(end).y = laneWidth/2;
        cars(end).dir = 'left';
    elseif rand < 0.02
    elseif rand < 0.02
        % Up
        cars(end+1).x = rightOffset + laneWidth/2;  % Right lane
        cars(end).y = -mainLength/2 - 10;
        cars(end).dir = 'up';
    elseif rand < 0.02
        % Down
        cars(end+1).x = leftOffset - laneWidth/2;   % Left lane
        cars(end).y = mainLength/2 + 10;
        cars(end).dir = 'down';
    end

Answer 1

[Harsh]

Hi @BASHIR,

This looks like an interesting project, using MATLAB Copilot in MATLAB R2025a I have made the following changes to the script:

• Each junction (leftJunction, rightJunction) now has its own state machine (EW_GREEN, EW_YELLOW, NS_GREEN, NS_YELLOW) and timers.
• Variables like countLW (Left West), countLS (Left South), etc., track car densities for all 8 approaches.
• Lights switch based on comparing car counts on green vs. red approaches, after a minimum green time.
• Lights are now hLightLW, hLightLS, etc., for easier identification.
• Cars now check the specific light for their direct path of approach.
• The traffic light visuals are positioned more appropriately for each approach.
• Initial and random car spawning is more structured, though you might want to expand it to ensure all 8 approaches are consistently fed with traffic for more dynamic testing.
• A simple leftJunctionLocked and rightJunctionLocked mechanism is kept to prevent multiple cars from being in the absolute center of the junction simultaneously.
• Cars and their graphical rectangles are now linked by a UserData ID for more robust removal and updating.

I believe these changes have been successful in increasing the efficiency of the traffic signal network. As you can see in the following image the traffic signals are working as expected.

PFA the modified ".m" script.

I hope this helps, thanks!