Final answer:
When making a left turn from a stop sign onto a main road, the primary duty is to ensure safety by checking for traffic, obeying speed limits, and yielding to others, with traffic signals further enhancing safety.
Step-by-step explanation:
The biggest duty owed when making a left turn from a stop sign onto a main road is ensuring the safety of all road users, including pedestrian safety and the safety of other motorists.
This involves checking for oncoming traffic from all directions, obeying the speed limits, and yielding to pedestrians and other vehicles that have the right of way. Installing a traffic signal can further enhance safety by regulating the flow of traffic and providing clear instructions for when it's safe to cross or turn.