opencv road line detection with HoughLines - c++

Question

Hello I have an image simple street image
I want to detect road lines like here
but so far I just can do this
I don't understand what I am doing wrong this is my code, I need to this HoughLines
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/imgproc.hpp"
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
// Declare the output variables
Mat dst, cdst, cdstP;
// Loads an image
Mat src = imread( "/Users/user/Desktop/opencv_tests/street_scene.png", IMREAD_COLOR );
Canny(src, dst, 700, 500, 3);
// Copy edges to the images that will display the results in BGR
cvtColor(dst, cdst, COLOR_GRAY2BGR);
cdstP = cdst.clone();
// Standard Hough Line Transform
vector<Vec2f> lines; // will hold the results of the detection
HoughLines(dst, lines, 1, CV_PI/30, 75, 0, 0 );
// Draw the lines
for( size_t i = 0; i < lines.size(); i++ )
{
float rho = lines[i][0], theta = lines[i][1];
Point pt1, pt2;
double a = cos(theta), b = sin(theta);
double x0 = a*rho;
double y0 = b*rho;
pt1.x = cvRound(x0 + 1000*(-b));
pt1.y = cvRound(y0 + 1000*(a));
pt2.x = cvRound(x0 - 1000*(-b));
pt2.y = cvRound(y0 - 1000*(a));
line( src, pt1, pt2, Scalar(0,0,255), 3, LINE_AA);
}
imshow("Source", src);
waitKey();
return 0;
}