ELI5 Traffic Lights - why not use pressure sensors?

ELI5 Explain Like I'm 5: Bite sized answers to stuff you should know about - in a mini podcast

How intelligent are traffic light systems? What sensors are used? Why not use pressure sensors under the pavement? How do traffic systems coordinate across intersections in a city? Do emergency services like fire trucks and ambulances have the ability to control traffic signals?

... we explain like I'm five

Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: anthonypalumbo, blipsman, powerclean, nagisan and bigredinmass.

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