Question

this is my example http://gidzior.net/map/v3_animate_marker_directions.html (i’m using placeholder in the input), thx for the GM code to geocodezip.com here

in my example i’m using Google Maps API 3, is it possible set only main streets in the direction routes ?

    var map;
  var directionDisplay;
  var directionsService;
  var stepDisplay;
  var markerArray = [];
  var position;
  var marker = null;
  var polyline = null;
  var poly2 = null;
  var speed = 0.000005, wait = 1;
  var infowindow = null;
  var zoomed;

    var myPano;   
    var panoClient;
    var nextPanoId;
  var timerHandle = null;

function createMarker(latlng, label, html) {
// alert("createMarker("+latlng+","+label+","+html+","+color+")");
    var contentString = '<b>'+label+'</b><br>'+html;
    var marker = new google.maps.Marker({
        position: latlng,
        map: map,
        title: label,
        zIndex: Math.round(latlng.lat()*-100000)<<5
        });
        //marker.myname = label;
        // gmarkers.push(marker);

    /*google.maps.event.addListener(marker, 'click', function() {
        infowindow.setContent(contentString); 
        infowindow.open(map,marker);
        });*/
    return marker;
}


function initialize() {
  infowindow = new google.maps.InfoWindow(
    { 
      size: new google.maps.Size(150,50)
    });
    // Instantiate a directions service.
    directionsService = new google.maps.DirectionsService();

    // Create a map and center it on Warszawa.
    var myOptions = {
      zoom: 13,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    }
    map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);

    address = 'warszawa'
    geocoder = new google.maps.Geocoder();
    geocoder.geocode( { 'address': address}, function(results, status) {
       map.setCenter(results[0].geometry.location);
    });

    // Create a renderer for directions and bind it to the map.
    var rendererOptions = {
      map: map
    }
    directionsDisplay = new google.maps.DirectionsRenderer(rendererOptions);

    // Instantiate an info window to hold step text.
    stepDisplay = new google.maps.InfoWindow();

    polyline = new google.maps.Polyline({
    path: [],
    strokeColor: '#FF0000',
    strokeWeight: 3
    });
    poly2 = new google.maps.Polyline({
    path: [],
    strokeColor: '#FF0000',
    strokeWeight: 3
    });
  }



    var steps = []

    function calcRoute(){

if (timerHandle) { clearTimeout(timerHandle); }
if (marker) { marker.setMap(null);}
polyline.setMap(null);
poly2.setMap(null);
directionsDisplay.setMap(null);
    polyline = new google.maps.Polyline({
    path: [],
    strokeColor: '#FF0000',
    strokeWeight: 3
    });
    poly2 = new google.maps.Polyline({
    path: [],
    strokeColor: '#FF0000',
    strokeWeight: 3
    });
    // Create a renderer for directions and bind it to the map.
    var rendererOptions = {
      map: map
    }
directionsDisplay = new google.maps.DirectionsRenderer(rendererOptions);

        var start = document.getElementById("start").value;
        var end = document.getElementById("end").value;
        var travelMode = google.maps.DirectionsTravelMode.DRIVING

        var request = {
            origin: start,
            destination: end,
            travelMode: travelMode
        };

        // Route the directions and pass the response to a
        // function to create markers for each step.
  directionsService.route(request, function(response, status) {
    if (status == google.maps.DirectionsStatus.OK){
    directionsDisplay.setDirections(response);

        var bounds = new google.maps.LatLngBounds();
        var route = response.routes[0];
        startLocation = new Object();
        endLocation = new Object();

        // For each route, display summary information.
    var path = response.routes[0].overview_path;
    var legs = response.routes[0].legs;
        for (i=0;i<legs.length;i++) {
          if (i == 0) { 
            startLocation.latlng = legs[i].start_location;
            startLocation.address = legs[i].start_address;
            // marker = google.maps.Marker({map:map,position: startLocation.latlng});
            marker = createMarker(legs[i].start_location,"start",legs[i].start_address,"green");
          }
          endLocation.latlng = legs[i].end_location;
          endLocation.address = legs[i].end_address;
          var steps = legs[i].steps;
          for (j=0;j<steps.length;j++) {
            var nextSegment = steps[j].path;
            for (k=0;k<nextSegment.length;k++) {
              polyline.getPath().push(nextSegment[k]);
              bounds.extend(nextSegment[k]);



            }
          }
        }

        polyline.setMap(map);
        map.fitBounds(bounds);
//        createMarker(endLocation.latlng,"end",endLocation.address,"red");
    map.setZoom(18);
    startAnimation();
    zoomed=false;
    }                                                    
 });
}



      var step = 50; // 5; // metres
      var tick = 100; // milliseconds
      var eol;
      var k=0;
      var stepnum=0;
      var speed = "";
      var lastVertex = 1;


//=============== animation functions ======================
      function updatePoly(d) {
        // Spawn a new polyline every 20 vertices, because updating a 100-vertex poly is too slow
        if (poly2.getPath().getLength() > 20) {
          poly2=new google.maps.Polyline([polyline.getPath().getAt(lastVertex-1)]);
          // map.addOverlay(poly2)
        }

        if (polyline.GetIndexAtDistance(d) < lastVertex+2) {
           if (poly2.getPath().getLength()>1) {
             poly2.getPath().removeAt(poly2.getPath().getLength()-1)
           }
           poly2.getPath().insertAt(poly2.getPath().getLength(),polyline.GetPointAtDistance(d));
        } else {
          poly2.getPath().insertAt(poly2.getPath().getLength(),endLocation.latlng);
        }
      }


      function animate(d) {
// alert("animate("+d+")");
        if (d>eol) {
          map.panTo(endLocation.latlng);
          marker.setPosition(endLocation.latlng);
          return;
        }
        if (d>eol-1000 && zoomed!=true) {
          map.setZoom(15); // or whatever value
          zoomed=true;
        }
        var p = polyline.GetPointAtDistance(d);
        map.panTo(p);
        marker.setPosition(p);
        updatePoly(d);
        timerHandle = setTimeout("animate("+(d+step)+")", tick);
      }


function startAnimation() {
        eol=polyline.Distance();
        map.setCenter(polyline.getPath().getAt(0));
        // map.addOverlay(new google.maps.Marker(polyline.getAt(0),G_START_ICON));
        // map.addOverlay(new GMarker(polyline.getVertex(polyline.getVertexCount()-1),G_END_ICON));
        // marker = new google.maps.Marker({location:polyline.getPath().getAt(0)} /* ,{icon:car} */);
        // map.addOverlay(marker);
        poly2 = new google.maps.Polyline({path: [polyline.getPath().getAt(0)], strokeColor:"#0000FF", strokeWeight:10});
        // map.addOverlay(poly2);
        setTimeout("animate(50)",2000);  // Allow time for the initial map display
}

Answer 1

No. You have options avoidHighways and avoidTolls, but there’s nothing like avoidByways. This is because the service needs to get as close as possible to origin and destination and it may only be possible to use byways to get there. avoidHighways is possible because it’s highly likely there is some route from A to B without using a motorway. [An exception is where a motorway connects two islands and there is no minor road route: I don’t know if avoidHighways merely avoids them and the API would in fact use a highway if there is no alternative.]

The API will favour fast routes, so main streets will be preferred by default. If you were able to instruct the API to use only main streets, it is entirely possible that it would not be able to find directions between A and B.