Traffic often require consistency across municipalities or states so people who are blind or have trouble with their sight (and other reasons) can utilize the same type of infrastructure from city to city. It reduces liability to standarize a lot of things. That's why it's green yellow red on traffic lights and it's impossible for your city to make it blue/purple/pink.i'm not doubting that the regs exist; i'm questioning why something like that needs regs at a federal level.There are federal and state guidelines (design standards) for all traffic control devices. That includes all striping and signing. You'd be surprised at how much design goes into an intersection or striping a road. Google 'mutcd'.why do we need Federal laws regarding crosswalks?