Have you considered asking your son to pay it? After all, it was him who broke the traffic law and got caught doing it. That's how it works with MY kids - for parking tickets, tolls, and any other infractions they cause. Never had a complaint - they have always fessed up.
+1. This was my thought.
When I was working I drove through one of the highest volume intersections in California. (Mira Mesa Blvd and Scranton for those of you familiar with San Diego). It had a red light camera. When it was first installed the contractor received about 80% of the revenues from tickets... And the contractor was alleged to be shortening the yellow light time to increase the number of tickets. A successful lawsuit about this resulted in the revenue distribution changing. The contractor was switched to a fixed price maintenance contract, and no longer had incentive to increase the revenues. It still generated plenty of tickets - because a lot of people run that intersection... but at least the yellow light duration was reasonable after the contractor was busted.