Unfortunatly what you regard as dengerous does not count it is what the law says amounts to dangerous. In this case if the facts, as deduced from the evidence, simply could not, as a matter of law, amount to dangerous then the Judge is required to direct the jury to acquit.
What appears to be wrong here is that if careless driving could be established from the facts then this could be put to the Jury to decide.
I'm afraid that the CPS leave a lot to be desired in this and many other cases.