> could you just hotwire the lights themselves and bypass the controller?
Assume you're a bank robber... place a bug (e.g. a raspi with an lte dongle) in a cabinet somewhere, now you control all traffic lights in the city. Then when you do the heist, progressively turn each intersection you pass all-sides green, and dumbass drivers will do the rest and prevent the police from catching up with you.
At least here in Germany, IIRC there used to be a mandate for a "detect conflicting greens" hardware interlock - pretty simple, wire the green light powers to AND gates, and if they trigger, shut down the cabinet hard. Same for a red light burning out - measure the current on each red light power line, if it drops below a threshold, shut down everything else to avoid a driver not seeing any light and t-boning someone who legitimately has green.
But a system without such a hardware interlock will just happily do what is asked of it.
Assume you're a bank robber... place a bug (e.g. a raspi with an lte dongle) in a cabinet somewhere, now you control all traffic lights in the city. Then when you do the heist, progressively turn each intersection you pass all-sides green, and dumbass drivers will do the rest and prevent the police from catching up with you.
At least here in Germany, IIRC there used to be a mandate for a "detect conflicting greens" hardware interlock - pretty simple, wire the green light powers to AND gates, and if they trigger, shut down the cabinet hard. Same for a red light burning out - measure the current on each red light power line, if it drops below a threshold, shut down everything else to avoid a driver not seeing any light and t-boning someone who legitimately has green.
But a system without such a hardware interlock will just happily do what is asked of it.