So you’re driving home from Grandmother’s house. When, bam! You hit a yellow light. Before you know it, the light’s turned red. And you’ve gotten a ticket.

The National Motorists Association says cities are trimming the timing on yellow lights so they skip right to red.

John Bowman, the association’s spokesman, says, “It’s a rigged system and they’re doing it to increase their camera revenues.”

He points out, for example, that all of Chicago’s yellow lights last three seconds — even where traffic is going more than 40 miles an hour. Bowman says the city earns more than $70 million a year from red light cameras.

But state and local governments say the cameras’ primary purpose is traffic safety.

“The notion by some that there’s some sort of devious conspiracy when communities put cameras into place really isn’t true,” says Jonathan Adkins with the Governors Highway Safety Association.    

There is no federal referee in this debate. Local governments decide how long their yellow lights should be. The Federal Highway Administration only issues guidelines that they should last three to six seconds.