[YeahSureWhyNot]

its federally mandated to be between 3 to 6 seconds. towns are free to choose anything in between. some towns that had 5 second yellow lights will change it to 2 seconds after installing a red light camera and make good amount of money from locals who knows the length of the yellow and attempt to blow thru

[kolinko]

So cities change timings in an illegal way? How is this possible :O

[YeahSureWhyNot]

no, typo. they basically change it within limits just to get drivers trapped