<script>
        function initialize() {
            var map = new google.maps.Map(document.getElementById('map_canvas'), {
                zoom: 8,
                center: new google.maps.LatLng(22.304634, 73.161070),
                mapTypeId: google.maps.MapTypeId.ROADMAP
            }),
       directions = new google.maps.DirectionsService(),
       displayer = new google.maps.DirectionsRenderer({
            draggable: true
        });

            displayer.setMap(map);
            directions.route({
                origin: new google.maps.LatLng(22.304634, 73.161070),
                destination: new google.maps.LatLng(23.022242, 72.548844),
                travelMode: google.maps.DirectionsTravelMode.DRIVING
            }, function (result) {
                displayer.setDirections(result);
            });
        }
        google.maps.event.addDomListener(window, 'load', initialize);
        google.maps.event.addListener(displayer, 'directions_changed', some_method);
    </script>