I think the common complaint here is that there are plenty of "crimes" that are committed on a daily basis like minor speeding (going 1-5 mph over the speed limit), jaywalking, etc, that are nearly impossible to entirely enforce. This gives police the ability to selectively enforce said laws simply because they can't totally enforce it. As you noted this can be used to punish the poor far more than others. The combination of all of these factors and the ability to track these "offenders" down more easily, it isn't a far shot from what the parent poster was saying by comparing it to a debtors' prison.
Worth asking: Why do they punish the poor more so than others?
I really doubt it's because those in poverty give fewer fucks about following traffic law.
I doubt it's a matter of education since you're supposed to demonstrate that minimum competence before you get a license anyways, and if you're not, we've found the problem.
I believe you're looking at the wrong part of the equation. It's not about the relative rates of traffic violations among the poor vs everyone else; it's about the relative impact the same fine has.
If you have comfortable amounts of wealth and/or income and get hit with a $500 fine you might be annoyed but you can pay it and go on your way.
But for the poor it's not so simple. First, that $500 represents a much larger burden. Even if they do scrape together the money to actually pay the fine, it might mean other bills would have to go unpaid, for example. And if they don't or can't get the money to pay the fine, those outstanding fines can get additional fees tacked on like Vigilant's 25%.
So it's not about seeking out the poor disproportionately more than the rich; it's about how the same punishment is actually more punishing.
I can accept that, but then we're left right back where we started.
Income based fines would be (rightly) struck down based on the equal protection clause to the constitution. They might even survive introduction to state legislation, but the moment someone with the resources contests it, it'll fall.
Not having the fines is not tenable, seeing as how it's the only way the law has any teeth.
Between a rock and a hard place. And seeing as how these laws are generally to society's benefit, just dropping them isn't valid either.
If the fine is an equal percentage for all, one could make a compelling constitutional argument that it applies equally to all. The same argument has been made against progressive tax and have been ruled without merit.