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. To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: ELI5ThePodcast@gmail.com