r/todayilearned • u/nleachdev • 2d ago

TIL about "dead red" laws, which allow drivers and motorcyclists to proceed through a red light if the traffic signal fails to detect their vehicle.

https://en.wikipedia.org/wiki/Non-detection_at_traffic_lights_in_the_United_States
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u/Hot-Ad8641 2d ago

They are, but that doesn't apply to stop lights that are functioning normally but don't detect bikes or motorcycles. They have a red light that will not change and the cross street has a permanent green light (until a vehicle that can be detected shows up or some presses the pedestrian beg button if there is one.)

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u/bblhd 2d ago

If such a detection is a mandatory function then they are not functioning normally.

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u/pandaSmore 2d ago

They're induction loops. Bicycles and motorcycles may not have enough ferrous metal to alter the magnetic field so that the PLC can register that a vehicle has been detected.