What is the primary consideration when designing vehicle detection for a protected-permissive left-turn phase?

1. The detection zone must only cover the left-turn lane stop bar area
2. Both stop-bar presence detection and advance detection are needed — stop-bar for gap-out during permissive and advance for queue measurement during protected
3. Only advance detection is needed for left-turn phases
4. Detection is not needed for left-turn phases because they operate on fixed timing