I'm thinking of semi-directly causing a very serious car accident
That seems very concerning. Have you just thought of it recently?
No, I've planned it for a while now.
Causing a serious accident on purpose is wrong. You should always follow the laws of the road while driving.
Yeah, I 'feel' it's morally wrong but what happens if I do get caught and seriously injured.
If you got caught, then you will end up in jail and have a really high bond, so I do not suggest you do it. And as you've said you can also get seriously injured, so I think you know the risks here and I seriously strongly recommend that you just be safe out there and keep your distance with other cars on the road.