function initialize_trucks() {
	if ( map_options.crew_truck_icon == '' )
		return;	// Don't display trucks.

	var trucks = viewer_data.trucks.length;
	for ( var i = 0; i < trucks; i++ ) {
		var truck = viewer_data.trucks[i];
		var description =
			'<ul><li><b>' + truck.VehicleName + '</b></li>' +
			'<li>Type: <b>' + truck.Type + '</b></li>' +
			'<li>Speed: <b>' + truck.Speed + '</b></li>' +
			'<li>Heading: <b>' + truck.Heading + '</b></li>' +
			'<li>Event Time: <b>' + truck.EventTime + '</b></li>' +
			'<li>Location: <b>' + truck.Location + '</b></li></ul>';
		add_truck(truck.Lat, truck.Lon, description);
	}
}

// Add a truck to the map.
function add_truck(lat, lon, description) {
	var	location = new OpenLayers.LonLat(lon, lat).transform(
		new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());
	var	symbol = new OpenLayers.Popup(null, location, new OpenLayers.Size(0, 0), "", false);
	map.addPopup(symbol);
	$(symbol.div).css({
		'overflow': 'visible',
		'margin-left': '-10px',
		'margin-top': '-10px',
		'height': '100px',
		'width': '100px',
		'background-color': 'transparent'
	}).html('<img src="' + map_options.crew_truck_icon + '" />');
	add_hover_popup(description, location, $(symbol.div).attr('id'));
	shape_ids.push(new Object);
	shape_ids[shape_ids.length - 1].icon = symbol;
}