If you wheel in CA you NEED to do this. Not only that, you NEED to pass this on and get more people to do it. (Actually, even if you don't wheel and just want to access to dirt roads in CA in Prius, you need to do this)
Not gunna bore you with all the details, but here's the jist of it: What happened on the Rubicon with the water board may now happen on all forest roads. They want to use waterboard rules and regulations to shut us off our land. Before you start making all the CA posts, don't worry, this is coming your way soon too.
This takes a little more than the normal effort, but here's the directions: