I was actually in the Teamsters for 5 years William. I didn't drive around all night though. I was considered a 'working Teamster' I was a highway guardrail installer. Making the highways safer for everyone who drives on them. At 6'0 and only 135 lbs though I think the guardrail outweighed me though.
I agree with Tony though also, California is most likely the only state that requires them. I have seen guys get kicked off of jobs for not having them on their trucks here.
If you have a back up alarm on your truck then it should be working. Just like if you have 100 lights on your truck, CHP can cite you for having just 1 of those 100 lights not working.