Using Google Maps API to get travel time data

from google.maps.DirectionsRenderer

Distance by using:

directionsDisplay.directions.routes[0].legs[0].distance.text

Duration by using:

directionsDisplay.directions.routes[0].legs[0].duration.text

The above answer is in violation of Google API terms of service, and hence, incorrect.

The Google Maps API only allows you to calculate travel time if it's referenced against a Google Map displayed to the user.

You can't use the API if you don't display a Google Map to the end user of the service.

Update:

Any answer here, that does not show the final results mapped on a google map, is in violation of the aforementioned terms of service and eventually, incorrect.

For the record: At this time (year 2015) GDirections, GLatLng, GEvent, etc. are deprecated.

---

You can use google.maps.DirectionsService class (Google Maps JavaScript API V3)

In the following snippet, location and target are objects containing latitude and longitude coordinates.

1) The google.maps.DirectionsService class admit both LatLng and string values to feed their origin and destination properties.
2) A LatLng is a point in geographical coordinates: latitude and longitude.

var origin = new google.maps.LatLng( location.latitude, location.longitude ); // using google.maps.LatLng class
var destination = target.latitude + ', ' + target.longitude; // using string

var directionsService = new google.maps.DirectionsService();
var request = {
    origin: origin, // LatLng|string
    destination: destination, // LatLng|string
    travelMode: google.maps.DirectionsTravelMode.DRIVING
};

directionsService.route( request, function( response, status ) {

    if ( status === 'OK' ) {
        var point = response.routes[ 0 ].legs[ 0 ];
        $( '#travel_data' ).html( 'Estimated travel time: ' + point.duration.text + ' (' + point.distance.text + ')' );
    }
} );

Yep, this is definitely possible using the API. You can construct a GDirections object without a map or directions div. You can do a load request from A to B and then call the getDuration method to get the total travel time.

First you need to create a directions object:

// no need to pass map or results div since
// we are only interested in travel time.
var directions = new GDirections (); 

Then do your load request to resolve the directions (I have used two latitudes and longitudes as my start and end points, but you can use addresses here as well):

var wp = new Array ();
wp[0] = new GLatLng(32.742149,119.337218);
wp[1] = new GLatLng(32.735347,119.328485);
directions.loadFromWaypoints(wp);

Then you need to listen for the load event so you can call getDuration once the directions have been resolved:

GEvent.addListener(directions, "load", function() {
    $('log').innerHTML = directions.getDuration ().seconds + " seconds";
        });

You can find the whole example here and the JavaScript here. You can check the Google Maps Documentation for more info about the options you can give the GDirections object (like walking distance etc...). You should also listen to the error event for geocoding failures.