// Declare the Directions Service
var directionsService = new google.maps.DirectionsService();
/**
* Use the Places Autocomplete Place IDs for the origin and
* destination to reduce chances of errors.
* The departure time is in milliseconds and MUST be in the future.
* Travel mode is Driving.
*/
var request = {
                origin: {
                    placeId: "ChIJyYfhZ79ZwokRMtXcL6CYxkA" }
                },
                destination: {
                    placeId: "ChIJvwJZrWH4wokRNBcFMQ0ohIE"
                },
                travelMode: google.maps.TravelMode.DRIVING,
                drivingOptions: {
                    departureTime: new Date(1447621200000),
                    trafficModel: google.maps.TrafficModel.BEST_GUESS
                }

directionsService.route(request, function(result, status) {
  // Check to see if the Service responded as expected
  if (status == google.maps.DirectionsStatus.OK) {
  var routesLegs = result.routes[0].legs[0];
  var durationText = routesLegs.duration.text;
  var durationInTrafficText = routesLegs.duration_in_traffic.text;
  var duration = routesLegs.duration.value;
  var durationInTraffic = routesLegs.duration_in_traffic.value;
    // Create a "Traffic Factor" score between typical and predicted travel times
    var trafficFactor = (durationInTraffic / duration);
} else {
    // Alert why the Directions Service Request failed.
    alert('Directions request failed due to ' + status);
}

"legs": [
        {
          "duration": {
            "text": "25 mins",
            "value": 1471
          },
          "duration_in_traffic": {
            "text": "28 mins",
            "value": 1687
          }
      ...