<?php wp_get_archives( array( 'type' => 'yearly', 'before' => '<li class="CAPS source-bold"><span class="plus">+</span> Trip ','after' => '</li>', 'format' => 'custom', ) ); ?>

<?php $linkstring = wp_get_archives(array('echo' => 0,'format'=>'custom','type'=>'yearly','before'=>'|'));
$linkarray = explode('|',$linkstring);
if ( get_option('permalink_structure') != '' ) {
  $pattern = '#/(dddd)/?[^>]+?>#';
} else {
  $pattern = '/m=(dddd)[^>]+?>/';
}

foreach ($linkarray as $onelink) {
  if (preg_match($pattern,$onelink,$matches)) {
      $mylink = 'Trip '.$onelink;
      $newlink = str_replace('>'.$matches[1], '><span class="plus">+</span> Trip '.$matches[1], $onelink);
     $output .= "<li class='$matches[1] archive-item' >$newlink</li>n";
  }
}

echo $output; ?>