title: How to overlay GeoJSON on OSM with OpenLayers?
body: <p>I am trying to create one map. I am using OSM as base layer and now I am trying to overlay my road network as GeoJSON. There is no error in my code (Checked by Firebug). I can view nice map of OSM but problem is there is not any road network on my OSM map. I do not know what I have done worng. Bellow, I have given my code.</p>
  
  <p>I used following command to create GeoJSON from my console. I am using OSGeo Live (Ubuntu).</p>
  
  <pre><code>$ ogr2ogr -f "GeoJSON" roads.json roads.shp roads
  </code></pre>
  
  <p>JavaScript Code----</p>
  
  <pre><code>//OSM Layer-----------------------------------------------
  var map = new OpenLayers.Map('map');
  var layer = new OpenLayers.Layer.OSM( "Simple OSM Map");
  map.addLayer(layer);
  
  //GeoJSON Layer-------------------------------------------
  var vector_format = new OpenLayers.Format.GeoJSON({}); 
  var vector_protocol = new OpenLayers.Protocol.HTTP({
      url: 'ml/roads.json',
      format: vector_format
  });
  var vector_strategies = [new OpenLayers.Strategy.Fixed()];
  var vector_layer = new OpenLayers.Layer.Vector('More Advanced Vector Layer',{
      protocol: vector_protocol,
      strategies: vector_strategies 
  });
  
  map.addLayer(vector_layer);
  
  //Projection-----------------------------------------------
  map.setCenter(
      new OpenLayers.LonLat(18.068611, 59.329444).transform(
          new OpenLayers.Projection("EPSG:4326"),
              map.getProjectionObject()
      ), 10
  );
  </code></pre>
  
  <p>Thanks, in advance.</p>