Index: functions.php
===================================================================
--- functions.php	(revision 25007)
+++ functions.php	(working copy)
@@ -142,6 +142,11 @@
 	 */
 	wp_enqueue_script( 'twentytwelve-navigation', get_template_directory_uri() . '/js/navigation.js', array(), '1.0', true );
 
+	/*
+	 * Adds JavaScript for toggling the sub-menu when :focus an anchor in a wp_nav_menu
+	 */
+	wp_enqueue_script( 'twentytwelve-nav-menus', get_template_directory_uri() . '/js/nav-menus.js', array( 'jquery' ), '1.0', true );
+
 	$font_url = twentytwelve_get_font_url();
 	if ( ! empty( $font_url ) )
 		wp_enqueue_style( 'twentytwelve-fonts', esc_url_raw( $font_url ), array(), null );
Index: js/nav-menus.js
===================================================================
--- js/nav-menus.js	(revision 0)
+++ js/nav-menus.js	(revision 0)
@@ -0,0 +1,21 @@
+/**
+ * nav-menus.js
+ *
+ * Handles toggling the sub-menu on the anchor focus (Accessibility)
+ */
+( function( $ ) {
+	$( 'li.menu-item a' ).on({
+		focus : function( e ) {
+			if( $( this ).parents( 'li' ).find( '> ul' ) ) {
+				$( this ).parents( 'li' ).find( '> ul' ).each( function() {
+					$( this ).show();
+				});
+			}
+		},
+		focusout : function( e ) {
+			if( $( this ).parents( 'li' ).find( '> ul' ).is( ':visible' ) ) {
+				$( this ).parents( 'li' ).find( '> ul' ).css( 'display', '' );
+			}
+		}
+	});
+} )( jQuery );
\ No newline at end of file