Possible Clues:

• Sue Grafton's ''--- for Evidence''
• Frozen water: Ger.
• Cologne cubes?
• It might halt traffic on the Rhein
• Grafton's "___ for Evidence"
• Danger on der Autobahn
• ___ for elephant
• Winter hazard on the autobahn
• Hazard auf der Autobahn
• German winter hazard