What's the best way to save a one-to-many relationship in Linq2Sql?

class Person
{
    IList<Vehicle> Vehicle;
}

class Vehicle
{
    string Name;
    string Colour;
}

using (Db db = new Db())
{
    var newPerson = db.People.SingleOrDefault(p => p.Id == person.Id) ?? new SqlContext.Person();
    // Left to right stuff.
    newPerson.Name = person.Name;
    newPerson.Age = person.Age;

    if (newPerson.Id <= 0)
        db.People.InsertOnSubmit(newPerson);
    db.SubmitChanges();
}

using (Db db = new Db())
{
    var newPerson = db.People.SingleOrDefault(p => p.Id == person.Id) ?? new SqlContext.Person();
    // Left to right stuff.
    newPerson.Name = person.Name;
    newPerson.Age = person.Age;

    // add vehicles.
    Vehicle firstV = new Vehicle();
    firstV.Name = "some name";
    firstV.Person = newPerson; // need to do this to set the person Id on the vehicle.
    newPerson.Vehicle.Add(firstV);
    // now when you save the Person it should save the Vehicle list
    // if you set Cascade save update on the list. (not sure how to do that in L2S

    if (newPerson.Id <= 0)
        db.People.InsertOnSubmit(newPerson);
    db.SubmitChanges();
}