Have you seen green signs like this along the highway? The first time I encountered them, I wasn't sure of their purpose. Eventually I realized that they were designed to help highway maintenance crews by indicating what kind of center striping was ahead.
If I've interpreted this correctly, it marks the end of a no passing zone for oncoming traffic.
Welcome! I hope you'll join me for my Wednesday in Wyoming posts -- a chance to learn a little bit about the state I now call home. And, for more information about me and my books, please visit www.amandacabot.com.