Before opening a vehicle door after parking on the roadside, what is the mandatory safety precaution to prevent 'dooring' collisions with cyclists and passing vehicles?

1. Push the door wide open instantly and exit as rapidly as possible
2. Check interior and exterior rearview mirrors, look over the shoulder to confirm no oncoming cyclists or vehicles, and open the door slightly before exiting (Dutch reach method)
3. Honk the horn twice, then kick the door fully open
4. Rely solely on passengers in the back seat to tell you when to exit