Perverse incentives 101: in China it costs you a lot less money and trouble to kill someone with a car than to injure them... so drivers are known to "finish the job" on purpose. Think this is just China? In the US if you aren't drunk, you are VERY UNLIKELY to be charged with a crime for hitting a pedestrian or cyclist, no matter how egregious your driving. Long live King Car!

In fact if you aren't drunk and don't know the victim, in many jurisdictions THERE IS NO CRIME corresponding to "hit and injured/killed a cyclist or pedestrian"! Even if you think "car accidents" shouldn't be criminalized, it is very difficult to win a civil suit if there was never a corresponding criminal charge. You see bizarre situations like one case here in Silicon Valley where a very elderly man -- a lawyer of course -- jumped a curb and a planter, crushed two child pedestrians against the side of a building, and then SUED THEM in an attempt to avoid liability for their extensive hospital bills.

A movie plot really could employ the car-as-murder-weapon loophole.