What is the pedagogical purpose of teaching learners the '3-Second Rule' (Drei-Sekunden-Regel) for following distance on Swiss highways?

1. It represents the exact time required to shift gears from 1st to 5th
2. It provides an easily measurable time buffer that ensures safe following distance across varying speeds, accommodating human perception/reaction time and brake system latency
3. It is a fixed minimum gap that remains sufficient in snow, ice, and fog without any further increase
4. It is the maximum duration a turn indicator may remain on