I do like that, its suitably grim, BUT I wonder if its actually big enough to read from a car. You'd probably have drivers getting much too close, trying to read what it says on the tabard !
Once took a plain tabard and wrote 'Cr*p Rider,highly Dangerous!' and sent my friend out with it on, for a joke,strangely cars backed off.....dunno why!
Still like the 'Pass wide and Slow' as think this is more universal for all to understand,guess you could have 'Pass wide and slow,or my horse will sit on your bonnet!'
I stopped using it though as I was told drivers could use writing on high viz vests as an excuse when they hit you. They could say they were distracted by it.
However, I do love the emotion of the one you've posted.
I'm all for hi-viz, but one day, for a joke, I hacked out wearing some antique riding clothes I'd found in a charity shop. The jods dated back to about 1920, huge wings on the sides, a very long hacking jacket, a stock and a bowler hat.
I only went for a short hack round the block but crikey, you should have seen the car drivers faces, never mind slow down, they were all doing emergency stops!! They either thought I was a ghost, or the hunt were just round the corner, whatever it was it worked.
my friend had a " sit on my tail and i will sit on you bonnet" at the riding school the staff wrote poo picker no. 1/ 2/ 3/ 4 etc lol
The only problem with that hi viz jacket is there are some horrid people on the road that would be more bothered about their car being dented than the horse dying.