No need to sanitise type of relation member, since will only be a Node, Way, or Relation and not user-provided.
<tr>
<td>
- <%= h(relation_member.member_type.capitalize) %>
- <%= link_to relation_member.member_id.to_s, :action => relation_member.downcase.member_type, :id => relation_member.member_id %>
+ <%= relation_member.member_type.capitalize %>
+ <%= link_to relation_member.member_id.to_s, :action => relation_member.member_type.downcase, :id => relation_member.member_id %>
<% unless relation_member.member_role.blank? %>
as
<%= h(relation_member.member_role) %>