var frame = -1;
function start_animation() {
  setInterval('window.animation()', 1000);
}
function animation() {
  frame++;
  switch (frame) {
    case 0:
    document.getElementById('waitcar1').style.visibility = 'hidden';
    document.getElementById('waitcar2').style.visibility = 'hidden';
    document.getElementById('waitcar3').style.visibility = 'hidden';
    document.getElementById('waitcar4').style.visibility = 'hidden';
    document.getElementById('waitcar5').style.visibility = 'hidden';
    break;
    case 1:
    document.getElementById('waitcar1').style.visibility = 'visible';
    break;
    case 2:
    document.getElementById('waitcar2').style.visibility = 'visible';
    break;
    case 3:
    document.getElementById('waitcar3').style.visibility = 'visible';
    break;
    case 4:
    document.getElementById('waitcar4').style.visibility = 'visible';
    break;
    case 5:
    document.getElementById('waitcar5').style.visibility = 'visible';
    break;
    case 6:
    frame = -1;
    break;
  }
}