My Partner Xiangyi and I decide to choose traffic signal lights system to introduce to heptapods.
Traffic signal lights 🚥, are tools used in human civilization to direct traffic operation and ensure traffic security and order. Traffic lights are usually set at intersections, where two roads cross, with the same red, yellow, and green🔴 🟡 🟢lights hanging in on all the sides of the intersection.
Signals for motor vehicles and no-motor vehicles 🚗:
Such signals are meant for vehicles. In traffic light with arrows responding the direction, there are 3 lights showing to the left⬅️, forward⬆️and right➡️, while in the traffic light with circular lights, the three lights from left to right correspond to left, forward and right in turn. The red light means no passing, that the corresponding direction is not allowed to proceed once the red light is on. Conversely, the green light indicates passage permitted. The yellow light shows a warning that the light is about to change from green to red, alerting oncoming traffic to slow down.
Pedestrian crossing signals🚶♀️:
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Pedestrian traffic signals are often set on the four intersecting roads, adjacent to the vehicle traffic lights, with two corresponding signals for each road, eight in total. It is used to guide pedestrians through the intersection with rules basically the same as above. However, in such traffic signal lights, there are only two states-stop and forward without need to turn, so instead of showing 3 different directions, the shape of the pedestrian lights simulate human posture, with red no-passing pattern showing pedestrians in a standing position, and the green permitting pattern showing pedestrians walking.
Rationale for color selection:
According to optical principles, red lights has a long wavelength, penetrates air well, and attracts more attention than other signals, so it is used to convey prohibition. Green is used as a pass signal, because red and green are the most different, therefore easy to distinguish. In addition, for humans, red expresses strongest hot or intense feeling, followed by yellow, while green has a cool and calm connotation. Therefore, people often use red to represent danger🚫, yellow to represent warning⚠️, and green to represent safety✅.
Some other general information
In addition, on many traffic lights, in order to remind pedestrians and vehicles to be careful, a countdown timer is set to show the remaining time before the color of the light switch, so that people can get ready ahead of time.
In different cases:
Such traffic light system is designed base on human beings’ body structure, that our visual organs grow on one side of our body, so only the side that can be observed by our eyes, that is, the part our body is facing, can be regarded as the “front”. However, as Ted Chiang described in “Story of Your Life”, the hetapods have completely different body structure- radially symmetric, use seven limbs to sense the surroundings, and seven eyes ringed to see. This may cause the traffic light system quite confusing to hetapods, since every side around means front to them, so they might receive much traffic light information from more than one direction at the same time( like a panoramic photo). But anyway, the rule remains the same: always follow the green lights and stop at the red ones.
