Re: @John Robson Mast Needed
I drive a recumbent most of the time, and a flag or mast makes neglibible difference to visibility to motorists.
I dont' see many flags/masts here: Google images
I've been commuting by 'bent for 7 years now, and my worst incident occured when I had colourful 2" wide 6' long kite streamers on a fishing whip and an 18" england flag at the driver's eye level as well as being lit up like a proverbial christmas tree. The driver looked straight at me and failed to see me...
The issue is that motorists look for cars, not clear tarmac. That's why there are so many "SMIDSY" incidents with motorbikes, cyclists and pedestrians. If you claim you can't see this box-on-wheels then how do you avoid concrete blocks in the road?
How do you avoid dogs?
How do you avoid children?
Besides which this thing would only occasionally be crossing a road, so most of the time it should be safe from motorists, except that they can't seem to keep between the kerbs - motorists in the UK kill 40-60 people a year on pavements (this even excludes crossings where the pedestrian has priority)