The main route for the traffic from Bremen to Köln is the autobahn A1
due to the heat and the road surface being very old,the road surface
between the exit HAGEN-NORD and WESTHÖFENER–KREUZ
has rillen and holes with a depth of over 20cm,
DUE TO THE ABOVE the road will be closed between the two points
above, a diversion is sign posted , follow the little blue signs with the
U plus a no in the box this will bring you back on to the autobahn at the next
junction, THE road is closed until Friday 0600hr but this could change if
they get any problems
20 cm’s 
Thats about 8 inches.
There handy them pre signposted diversion routes - Used them quite a few times when theres been tailbacks, accidents etc… 
IT has now been posted that this strectch of road will remain closed until the 3rd of Augest, as the repairs are takeing a longer due to the damage,