function btBusRollover() {
	document.getElementById("bt_bus").onmouseover = function() {
		document.getElementById("bt_bus").setAttribute("src", "./images/bt_shuttlebus_over.png");
	}
	document.getElementById("bt_bus").onmouseout = function() {
		document.getElementById("bt_bus").setAttribute("src", "./images/bt_shuttlebus.png");
	}
}
if(window.addEventListener) {
	window.addEventListener("load", btBusRollover, false);
}
else if(window.attachEvent) {
	window.attachEvent("onload", btBusRollover);
}