A concept that could possibly penetrate the bike-resenting mindset of many motorists, who continue to remain entrenched in their "get off the road" mentality:
MORE GAS FOR YOU
Emblazoned on the back of a jersey.
Hm? Would they get it?
Probably not. Most of the cagers who harass cyclists are operating at close to 100% of their brain's capacity already; that's why they can't drive straight after they yell, "Get on the sidewalk!" (regardless of the existence of a sidewalk at that spot). There's just not enough intellect left to process a concise, witty slogan.