During the days of "55"...I used to make commutes home to Houston for a couple of weeks while I was stationed in SD back in the 80's...
I'd come over the peak (San Diego County) on that drive and be heading back down right into San Diego with a good head of steam going...And a SD County (twice, separtate trips) would pull along side me and he'd flash me the "five finger salute" (twice)...
A friendly rolling reminder to get my head on straight before getting further into town...
The first time was a real surprise
...The second time 
I was thinking..."You guys are serious about that???"No stops, no tickets, just a well received reminder after a long time on the road...
I guess it was the tags, and deducing I was in the military, not that that is an excuse...