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cover of episode How do stoplights know when to change?

How do stoplights know when to change?

2025/6/4
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Moment of Um
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J
Jerry Kotsmacher
S
Sandon Totten
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Sandon Totten：我经常遇到红灯，导致我为修剪鼻毛而迟到，这让我非常苦恼。我一直好奇交通信号灯是如何知道何时变换颜色的。我了解到，交通信号灯的变色并非随意，而是基于一定的技术原理和交通流量的考量。车辆中的金属会干扰感应线圈中的电流，从而触发信号灯的变化。但即使车辆发送了信号，绿灯也可能需要一段时间才能亮起，因为可能存在大量反向交通。 Jerry Kotsmacher：我在明尼苏达州交通部工作，负责管理和维护大量的交通信号灯。交通信号灯主要通过两种方式来检测车辆并改变信号：一种是埋设在道路下方的感应线圈，另一种是安装在信号灯杆上的摄像头。感应线圈通过检测车辆的金属质量来判断是否有车辆需要通过，而摄像头则可以监控交通流量。此外，还有一些信号灯是定时控制的，它们会根据预设的时间间隔来切换颜色。如果车辆没有立即获得绿灯，可能是因为对向车道的交通流量较大，系统会优先保证主干道的通行效率。定时信号灯会根据不同方向的车流量分配不同的绿灯时间。

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Waiting for a stoplight to turn green can be really annoying, especially when you’re running late. It would be awesome if you had a magic wand you could wave to get the light to change. But alas, such things don’t exist. But how do stoplights know when to switch colors? We asked Jerry Kotzenmacher with the Minnesota Department of Transportation to help us find the answer.

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