Here are my thoughts:
1. Taxis - Sims can call a taxi to pick them up.
2. Jobs providing a car to go to work
3. Since this isn't an open world, cars should just be used to travel for a second and then loading screen.
4. Ability for teens to learn to drive in a rabbit hole. A secret skill would allow them to drive a car just like how the main object in the fitness stuff was implemented.
5. Normal Cars for normal sims, Vintage Cars, Luxurious Cars, etc.
6. Ability to wash the Car at home, repair the car, etc.
7. Garage
8. Ability to woohoo/mess around in the car and other romantic/friendly interaction.
9. School Bus for Teens and Children and maybe a bus, too.
10. Ability to drop and pick up Teens and Children at school in a rabbit hole. (This could appear on a message box asking if the sim should drop/pick up children at school).
That's all!
