It doesn't – and shouldn't – need prison, the point is to nudge drivers into safer more careful practices rather than letting bad practice become the norm and relying on chance to prevent bad outcomes (which is effectively what the current system does). That generally means modest fines and other inconveniences for even the minor offences but, of course, that requires road policing and for drivers to believe there's a chance of getting caught. Given the number of drivers I see speeding, using their phone, and other illegal activities, that's obviously not the case. There was an article the other day about 20-limits not working and the reason, of course, isn't that driving at a reduced speed isn't safer, but that simply people were not adhering to the limit and there's no enforcement. The message there isn't just that you can get away with it but that it's somehow not important or serious. Yes, it's obviously unfair to drivers, penalising them for breaking the law, but perhaps rather than keep the conservation about drivers, maybe we should ask how they feel about their own children and loved ones, or themselves being on the receiving end. There's a lot of othering, a lot of excuses, even down to the language were the driver is nearly always absent from crashes, their cars absently careening into each other and anyone who gets in the way. That's mostly, I think, because drivers don't want to accept that they're the causal agent and the responsibility that would entail.
