Because the vast majority of vehicle accident aren't criminal? Why would this be any different. If you've ever driven in Manhattan you'd know how easy it is for a mistake to happen, and it would be a mess to prove who's at fault since traffic laws and J walking are hardly enforced.
What is that even supposed to mean? Just because people don't intend to run over others doesn't mean it's not criminal when they do so through negligence. The phrase "if you've ever driven in Manhattan" seems to suggest you're well aware that plenty of drivers don't exactly reach to the level of competence we would expect from someone manuevering tons of steel in a dense city where the number of pedestrians frequently exceeds that of cars.
This line of thinking is exactly why we now have 300 deaths from traffic, or as many as murder cases. People think negligence in driving, be it speeding, fiddling with your phone, accelerating for that yellow and dodging instead of yielding to pedestrians in crosswalks are somehow excusable. They're not when you are driving a car.
Although I agree that this is certainly true, I cannot vouch for its historic truth. It is possible that the vast reduction in the murder rate is primarily due to the fact that vehicle accidents are (no longer) considered murder, rather than any actual reduction in violent crime.
Not stating this as fact -- I haven't even done my homework to look at vehicle-related deaths over time -- but as motivation for the possible blind spot pointed out by thrownaway2424. Historical crime data is notorious for this because statistics are gathered by law enforcement and have a subjective aspect based on the time that they are gathered.
There are always some subjective decisions on data reporting, but that's much more prevalent in data comparisons between countries rather than over time within a single country. The FBI has been very consistent in their reporting.
So the child who ran out chasing after a ball is your fault? The bicyclist wearing black, at night, in the rain, with no reflectors or lights is your fault?
We are human. We have moments of inattention ALL THE TIME. This is proven by many, many, many psychological studies. You don't convict someone of a crime because they committed an accidental error.
If you want to cut down on this, fund self-driving cars.
I would love to see a source for the claim that accidents are criminally prosecuted in Belgium.. The data I've found looks like ~5% of trips in Belgium are by drunk drivers, ~35% of Belgians drive over the speed limit, drivers only wear seat belts ~80% of the time and they aren't liable for their passengers' seat belt use..
It sounds like there should be thousands of Belgians in jail for traffic crimes, but extrapolating from their population / imprisonment rate (11.2M & 108/100k), it looks like they only have 12k total people in jail. Their annual violent crime rate is ~50/100k and if you assume even an average of a 2-year sentence for violent crimes, there is no room left in jail for these traffic criminals...
