Vehicle Speed Estimation via Blob Opencv C++

bool checkIfBlobsCrossedTheLine2(std::vector &blobs, int &intHorizontalLinePosition,int &intHorizontalLinePosition2, cv::Mat &imgFrame2Copy) {

bool blnAtLeastOneBlobCrossedTheLine = false;

for (auto blob : blobs) {



    if (blob.blnStillBeingTracked == true && blob.centerPositions.size() >= 2) {
        int prevFrameIndex = (int)blob.centerPositions.size() - 2;
        int currFrameIndex = (int)blob.centerPositions.size() - 1;



        if ((blob.centerPositions[prevFrameIndex].y > intHorizontalLinePosition && blob.centerPositions[currFrameIndex].y <= intHorizontalLinePosition)&&(blob.centerPositions[prevFrameIndex].y > intHorizontalLinePosition2 && blob.centerPositions[currFrameIndex].y <= intHorizontalLinePosition2)) {



        int time = 30;
        int distance = 200;

        int speed = distance/time;
        double dblFontScale = blobs[currFrameIndex].dblCurrentDiagonalSize / 10.0;
        int intFontThickness = (int)std::round(dblFontScale * 1.0);
        std::cout<<"Speed: "<<speed<<std::endl;

        cv::putText(imgFrame2Copy, std::to_string(speed), blobs[currFrameIndex].centerPositions.back(), CV_FONT_HERSHEY_SIMPLEX, dblFontScale, SCALAR_RED, intFontThickness);



            blnAtLeastOneBlobCrossedTheLine = true;
        }



    }

} 

return blnAtLeastOneBlobCrossedTheLine;

}

Please i didn't understand why i can't display the speed of each vehicle, so help please