I'll usually do it 3 times really quick same with the brakes if someones behind me and there is a cop hiding around a corner ahead.

Sometimes I get a puzzled look from across the highway but I find if I do it several times really quick the other driver usually figures out something is up. I know ppl have saved me a few times, so if I can help even one other person out at least someone can appreciate it, cause I can deal with getting flipped off and most ppl dont wana **** the guy in the jacked up diesel off anyway.

 

well I do my best to do the speed limit..and I really wish others would too...the speed limit is a limit for a reason... however i still flash my lights to warn the idiots who speed on purpose