At least in L.A.,most of the cops don't know the traffic laws for bicycles,traffic cops or not.They know so little about traffic laws for bicycles,I carry a copy of it for them to read when they hassle me.
When they want to see my ID,I also show them a copy of the bicycle laws for California.
If you saw me riding down the street and didn't know anything about bicycles,I'm guessing you would think I'm the homeless type.Long hair down to my waist,giant beard,greasy hair,dirty clothes( I do machine work for a living),rides a bike.....sounds homeless,even to me....
The way I look,the cops probably think I'm a homeless drunk and riding a stolen bike down the middle of the street and don't know it......