1. Many children get hurt *by cars* in school zones every year.

Question

2. Many children get hurt *by car* in school zones every year.
3. I went to school by my father's car.
[Which one is grammatical?]

Answer 1

Only #1 is correct.

In 2, you need "cars" -- like in 1.

3 should read, "I went to school in my father's car."