如何通过Google Maps API V3获得总驾驶距离？

var directionsService = new google.maps.DirectionsService();
var directionsRenderer = new google.maps.DirectionsRenderer();

var start = "New York, NY";
var end = "Washington, DC";

var request = {
  origin: start,
  destination: end,
  travelMode: google.maps.TravelMode.DRIVING
};

directionsService.route(request, function(result, status) {
  if (status == google.maps.DirectionsStatus.OK) {
    directionsRenderer.setDirections(result);
    var totalDistance = result.routes[0].legs[0].distance.text;
    console.log("Total distance: " + totalDistance);
  } else {
    console.log("Error: " + status);
  }
});

var mapOptions = {
  center: { lat: 40.7128, lng: -74.0060 },
  zoom: 8
};
var map = new google.maps.Map(document.querySelector("#map"), mapOptions);
directionsRenderer.setMap(map);