PLEASE HELP! I need to detect lines using Hough Transform

I need to detect road lanes using the Hough Transform. I'm using the image attached and I'm getting the following result. Can anybody help me detecting only the two road lines? Thanks in advance.

I  = imread('espe1_bn.jpg');

img_filt = imfilter(I, [-1 0 1], 'replicate','corr');
%subplot(2,2,2); imshow(img_filtro);axis on;
%title('Imagen filtrada');

% --Deteccion de bordes
BW = edge(img_filt,'canny');
%BW(BW < 0) = 0;
%BW(BW > 1) = 1;
[H,theta,rho] = hough(BW);
imshow(H,[],'XData',theta,'YData',rho,...
        'InitialMagnification','fit');
xlabel('\theta'), ylabel('\rho');
axis on, axis normal, hold on;
P = houghpeaks(H,2,'threshold',ceil(0.3*max(H(:))));
x = theta(P(:,2)); 
y = rho(P(:,1));
plot(x,y,'s','color','white');
lines = houghlines(BW,theta,rho,P,'FillGap',45,'MinLength',7);
figure, imshow(I), hold on
max_len = 0;
for k = 1:length(lines)
   xy = [lines(k).point1; lines(k).point2];
   plot(xy(:,1),xy(:,2),'LineWidth',2,'Color','green');

     % Plot beginnings and ends of lines
     plot(xy(1,1),xy(1,2),'x','LineWidth',2,'Color','yellow');
     plot(xy(2,1),xy(2,2),'x','LineWidth',2,'Color','red');

     % Determine the endpoints of the longest line segment 
     len = norm(lines(k).point1 - lines(k).point2);
     if ( len > max_len)
        max_len = len;
        xy_long = xy;
     end
  end

% highlight the longest line segment
plot(xy_long(:,1),xy_long(:,2),'LineWidth',2,'Color','cyan');

Output: