What is a key safety reason GDL programs encourage new drivers to practice freeway on-ramp merging with a supervising adult?

1. On-ramp merging requires matching freeway traffic speed and judging gaps, skills that need guided practice
2. Adults are legally required to take the wheel during merging
3. Merging is illegal for permit holders in all 50 states
4. Insurance policies are voided if a novice merges alone