[aggie]

Not everything can be solved with economic incentives. Do you really think people are making a conscious decision, "I'm not paying for it, might as well peel the top off my truck and grind my day/week to a halt because my employer is liable for damages"? If that was the case, they can just drive through the water wall too. This is an attention management issue -- does the driver realize they are too tall for the tunnel. Most will be caught with the initial flashing signs, but even those high-salience signs are somewhat 'normal' and thus possible to subconsciously ignore. The water wall is very out of the ordinary so it has a maximum likelihood of capturing attention.