Final answer:
The sign indicating the traffic flow option of either a left turn or proceeding straight in one lane, and a mandatory left turn in the adjacent lane, is referred to as 'Left or Straight'. This sign assists in traffic regulation and pedestrian safety at intersections.
Step-by-step explanation:
The sign indicating that traffic in one lane must turn left and traffic in the other lane has the option to turn left or go straight is described as option 2: Left or Straight.
This type of sign is designed to guide drivers on how they can proceed through the intersection. It indicates that the lane on the left is designated exclusively for left turns, while the adjacent lane offers drivers the flexibility to continue forward or make a left turn.
Safety measures such as traffic signals help regulate the flow of vehicles and enhance pedestrian safety by providing designated crossing times. This in turn helps in reducing speeding and potential accidents at intersections.