What does 'left in, right out' mean in Subject 1?

[DelReed]

Vehicles going straight have higher speed, so left-turning vehicles must yield to them. Left-turning vehicles follow traffic lights, while right-turning vehicles are generally not controlled by signals to avoid congestion at intersections, hence right-turning vehicles are required to yield to left-turning ones. Below are relevant explanations: 1. Arterial road: Refers to roads with wider lanes, higher traffic volume, complete safety and service facilities, and higher designated driving speeds. 2. Local road: Compared to arterial roads, these have narrower lanes, lower traffic volume, less complete safety and service facilities, and lower designated driving speeds. 3. Ramp: Also known as an approach, it refers to the connecting section between upper and lower roads of an interchange or viaduct, or the section connecting a highway with adjacent service roads.