Why is there traffic? How do traffic lights work? How do they know when to turn red and green? Why does green mean go and red mean stop? Why are cars able to go faster than they are allowed to go with the speed limit? Why do we drive on the right side of the road in the United States? Why are some roads bigger than others? Answers to your traffic questions with Mike Knodler, professor and director of the Transportation Center at the University of Massachusetts.
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- Traffic happens when lots of people are in the same place at the same time. If the number of vehicles is higher than the road can handle, you might get a traffic jam. But sometimes traffic slows because of the way people are driving.
- Traffic management systems like traffic signs and signals were developed as people moved into different modes of transportation, from walking to horse and buggies to the introduction of cars.
- Traffic lights have been around for over 100 years! They use lights to tell traffic from one direction to go, and tell cars in another direction to stop.
- Some traffic lights are on timers, so the light is green in one direction for a certain amount of time, then it switches to yellow and then red.
- Modern traffic lights are a combination of timers and sensors. A sensor might tell a traffic light that there’s a car waiting at the intersection and it needs to change. Multiple traffic lights can be linked together at intersections to make sure everyone goes at the right time.
- The next time you’re at an intersection, look for a sensor. It’s usually a metal box on the side of the road. That box contains a computer that keeps track of the intersection.
- If you’ve ever pushed a “walk” or pedestrian button at an intersection, that’s another example of a sensor. You are letting the traffic lights know to pause while a pedestrian crosses.
- Red is a warning color. In modern culture, red is often thought of as a signal of danger. But engineers discovered that it’s also more visible than other colors from farther distances. So it makes sense to have it be the color for a stop light.
- Red and green can be difficult for people who struggle to see all of the colors. So the positioning of the traffic lights is designed to be the same across all signals in the US: the red light is always on top, yellow is in the middle, and green is on the bottom. So if you can’t see the color but you can tell which light is on, you can still understand what the traffic signal is telling you.
- The tradition of driving on the right goes back to horse and buggy days.
