Leagal? maybe not
I cheated and used a cheap trick

I mounted 2 bycycle high intensity white lights in my crash bars they have 2 modes steady and rapid flashing a 1 watt LED ..
When I have to ride in remote county and outback areas in West Aus. I set them to flashing mode the result is brilliant although I believe illigal, so I switched them off in populated areas where the police lerk.
I find that all traffic suddenly reverts to the speed limit and moves left and any road user entering my space sits stationary until I pass day or night.. their faces are a picture
Having said this I am certain in W.A. it is questionable as to weither these are classed as mimicing an emergency vehicle.. but they are used on the road fitted to pedal cycles. My reason for fiting them was self preservation.