This I think will be my last comment in this thread:-
I WILL NOT put it it my car untill I am 100% sure it is working right.
I am sure you will not, but do you have the skills to know when it is safe? You might be 100% sure but do you have the knowledge / experience / test equipment for it actually to be 100% safe. I have been in electronics over 40 years, I would not attempt this project because I know some of what can go wrong, I know the testing I would have to do to make sure that the bits I know about would be safe. I don't know what special measures are also needed for automobile applications. Nor what tests are required to verify them.
The people that develop these work in large labs with a large budgets, masses of test equipment and a large bank of knowledge, experience and expertise.
One of the things I do know about is the testing you will have to do to prove the lack of susceptibility to electromagnetic interference. I don't have the equipment to do this and I suspect nether do you.
Lack of sufficient immunity could trigger faults, when say a motorcycle rides by.
I also don't know about what safety interlocks are required but I am dam sure some are required. Both in the hardware and software.
I am sure you would be very careful at first but remember most accidents with power tools happen not the first time they are used it is when you become familiar with them.
Come on, there are brakes ......
Yes, but it is often the surprise of something unexpected happening that prevents rapid corrective action, unfortunatly that is built into human beings. But it is not just you that is in danger, that would be fine (see what the Darwin Awards are all about), it is the danger to others, perhaps innocent bystanders that is the worry.
I did once drive to St Petersburg in 1990, I know the attitude to risk is quite different in your country. My biggest surprise was when two drunks riding one single bicycle pulled out in heavy fast moving traffic, right in front of me. If it wasn't a western car with an excellent breaking system I fear they would have been killed.