Permanent detour route to be used when the normal route is blocked. Follow the U&lt;number&gt; and go in the direction indicated by the arrow, to arrive at next crossing | roundabout | link with the 'normal' route.
<a href="//commons.wikimedia.org/wiki/User:Ad_Verburg" title="User:Ad Verburg">Ad Verburg</a>
<span class="int-own-work" lang="en">Own work</span>