Right i hate these so ive decided to set a few off on my bush bike. Do bikes set them off? I know where there are a couple on hills so i can get upto 30mph or over and hopefully waste some film. However, is there any way to tell if they have film in them? Dont want to waste my time and set off any that are empty. Thought about pulling a moonie as i speed through. That should piss some coppers off.