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Many cities try that. However it is very hard to pull that off when you have two way traffic, and busy cross streets make it worth. Two way traffic often means one direction has no cars, but the other does because the distance between lights is not something in control of the traffic engineers. And cross traffic means you need to handle the whole grid at once.
if she will go for it get a 100 pack of rubber or silicon rings (dollor store) they look nice from the distance strangers should look and no worry about lost rings and no safety worries.