Quartz:

I’ve discovered a life-saving device that allows cyclists to protect themselves and take back the road: the pool noodle. Use a bungee cord to strap this light, flexible toy to your bike rack so that it sticks out to the left side (or the right side, if you’re in a country where cars drive on the left). Start pedaling and watch as car after car moves over to the other lane.

Yeah, it may look silly and isn’t 100% effective but anything that increases the margin of safety is a good thing. Plus, it helps when you go jump in a lake. Thanks to John Gondor for the link.