The two drivers ended up in a dispute on the N15 between Heinerscheid and Niederfeulen just before 10 am on Wednesday.
One of the drivers pulled out a knife and stabbed the other motorist, before fleeing the scene. The perpetrator fled in a black VW with French license plates.
The police have appealed for any potential witnesses to contact the Diekirch/Vianden police station at (+352) 244-80-1000.
