It's the other way round:
Vehicle[] car = new Vehicle[N];
This makes more sense, as the number of elements in the array isn't part of the type of car, but it is part of the initialization of the array whose reference you're initially assigning to car. You can then reassign it in another statement:
car = new Vehicle[10]; // Creates a new array
(Note that I've changed the type name to match Java naming conventions.)
For further information about arrays, see section 10 of the Java Language Specification.