Remove unnecessary words

On a different note to my regular diatribe, passive voice can also make your writing more concise, strangely enough, by removing unnecessary words, i.e. information that isn’t required to get the message across or are unimportant.
“John Doe was hit by a car and then rushed to hospital.”
“John Doe and what happened to him is the focus of this sentence, not the thing that hit him.”
Additionally, it isn’t important how he got to a hospital, only that he’s there. (I’m particularly upset at ending a sentence with a preposition) 
This passive construction is much more efficient than;
“A car hit John Doe, and then an ambulance rushed him to a hospital,” which sounds as awkward as ‘passive’ sounds when ‘active’ should be used.
It isn’t vague like passive can be, but it isn’t concise, either. Another example is “John Doe was charged with the murder of his wife, Jane,” which sounds much simpler than “Police charged John Doe with the murder of his wife, Jane,” or even “Sergeant James Ryan charged John Doe with the murder of his wife, Jane,” where it isn’t clear whose wife Jane is. (or this one)

If writing a short story that only should contain 1500 words then you could look for the words that just add completeness like;

“John sat down and read a book.”  –  6 words

“John sat and read a book.”  –  5 words

There is sat down and stud up.