JSTS Buffered Polyline no serviço de rota (google maps V3)

Olá a todos, Não sei se alguém já viveu a mesma coisa que eu, trabalho com a API JSTS para criar um polígono que circunda a rota dos serviços do google mas o problema é que quando há cruzamentos na rota do polígono não pegue a distância fornecida, mas a superfície completa entre as duas estradas, a imagem a seguir [imagem o que eu quero e resultados do problema] explica o problema em detalhes, e aqui está o código usado.
Resultado e o que quer
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script><script src="https://maps.googleapis.com/maps/api/js?sensor=false"></script><script src="http://marocexpress.marocgeo.ovh/modules/trip/js/javascript.util.js"></script><script src="http://marocexpress.marocgeo.ovh/modules/trip/js/jsts.js"></script>

   <div id="map-canvas"></div>
  <div id="directions-panel"></div>

 <script type="text/javascript">
        var mapCanvas = "map-canvas";
    var map;
    var directionsService = new google.maps.DirectionsService;
    var directionsDisplay = new google.maps.DirectionsRenderer;
    var mapConfig = {
        zoom: 6,
        center: { lat: 32.082575, lng: -6.921387 },
        mapTypeId: google.maps.MapTypeId.ROADMAP,
        mapTypeControlOptions: {
            style: google.maps.MapTypeControlStyle.DROPDOWN_MENU,
            mapTypeIds: [google.maps.MapTypeId.HYBRID, google.maps.MapTypeId.ROADMAP, google.maps.MapTypeId.SATELLITE, google.maps.MapTypeId.TERRAIN]
        },
        overviewMapControl: true,
        scaleControl: true,
        streetViewControl: true,
        panControl: true,
        rotateControl: true,
        maxZoomForCenter:17
    };

function initialize() {
    map = new google.maps.Map(document.getElementById(mapCanvas),mapConfig);
    directionsDisplay.setMap(map);
    calculateAndDisplayRoute(directionsService, directionsDisplay);
};

function calculateAndDisplayRoute(directionsService, directionsDisplay) {
    var waypts = [];
    var checkboxArray = document.getElementById('waypoints');

    waypts.push({
        location: new window.google.maps.LatLng(33.494873,-7.718875),
        stopover: true
    });

    waypts.push({
        location: new window.google.maps.LatLng(33.595501,-7.578152),
        stopover: true
    });


    directionsService.route({
      origin: new window.google.maps.LatLng(33.563656, -7.636282),
      destination: new window.google.maps.LatLng(33.477188, -7.945458),
      waypoints: waypts,
      optimizeWaypoints: true,
      travelMode: 'DRIVING'
    }, function(response, status) {
      if (status === 'OK') {
        directionsDisplay.setDirections(response);
        var route = response.routes[0];

        var legs = response.routes[0].legs;
        overviewPath = response.routes[0].overview_path,
        overviewPathGeo = [];
        for (var i = 0; i < legs.length; i++) {
          var steps = legs[i].steps;
          for (j = 0; j < steps.length; j++) {
             var nextSegment = steps[j].path;
             for (k = 0; k < nextSegment.length; k++) {
                 overviewPathGeo.push(
                   [nextSegment[k].lng(), nextSegment[k].lat()]
                 );
            }
          }
        }
        bermudaTriangle = new google.maps.Polygon({
              paths: createPolygon(overviewPathGeo),
              fillColor: '#ff0000',
        });
        bermudaTriangle.setMap(map);

        var summaryPanel = document.getElementById('directions-panel');
        summaryPanel.innerHTML = '';
        // For each route, display summary information.
        for (var i = 0; i < route.legs.length; i++) {
          var routeSegment = i + 1;
          summaryPanel.innerHTML += '<b>Route Segment: ' + routeSegment +
              '</b><br>';
          summaryPanel.innerHTML += route.legs[i].start_address + ' to ';
          summaryPanel.innerHTML += route.legs[i].end_address + '<br>';
          summaryPanel.innerHTML += route.legs[i].distance.text + '<br><br>';
        }
      } else {
        window.alert('Directions request failed due to ' + status);
      }
    });
  }

  createPolygon = function(overviewPath) {
    if(overviewPath && overviewPath.length>= 0){
        last_width_long = 7;
        var distance = last_width_long / 1000;  //en km.
        distance = (distance / 111.12);
        geoInput = {
            type: "LineString",
            coordinates: overviewPath
        };
        var geoReader = new jsts.io.GeoJSONReader(),
            geoWriter = new jsts.io.GeoJSONWriter();
        var geometry = geoReader.read(geoInput).buffer(distance);
        var polygon = geoWriter.write(geometry);
        polygon_route = polygon;

        var areaCoordinates = [];
        var polygonCoordinates = polygon.coordinates[0];
        for (i = 0; i < polygonCoordinates.length; i++) {
            var coordinate = polygonCoordinates[i];
            areaCoordinates.push(new google.maps.LatLng(coordinate[1], coordinate[0]));//set latitude a
        }
        return areaCoordinates;
    }else return false;
    };
   google.maps.event.addDomListener(window, 'load', initialize);
  </script>

</code>