It's not legal in Ca. to use 4 way flashers unless an emergency. However, most cops overlook it you use them to warn of being slow going up-hill. Jimmy
May 26, 2010 Rating
Why California truckers don't use their flashers by: Hervy
The DOT in California doesn't want truckers to use the flashers. If you're asking why they don't, I can't tell you but they will write a ticket for it if they feel like it.