Express frustration with the behavior of slow-moving vehicles on highways and compare it to the importance of speeding tickets in road safety.
I wish the cops would be even somewhat as zealous about ticketing these idiots as they are about getting speeders.  It is a major source of road rage - especially when it is an 18-wheeler moving 2 km/hr faster than the 18 wheeler going 98 km/hr in the right lane.  Better to bust cars going over 120 km\hr on highways designed for cars to go at least that fast.  Ridiculous - it only encourages other drivers to take additional risks to get around them.