Even though there are only a few OFFICIAL single rider lines, I have been able to shorten my wait on a recent solo trip. A cast member gave me this tip. She said to mention it to the cast members whenever you get a chance or hold up a finger indicating number 1 whenever I saw a cast member in the line. I was able pulled out of line on a number of rides including Space Mountain, Big Thunder, and Splash Mountain and brought right up to the front to fill in a gap. It really shortened my waits considerably on lots of the non-SRL attractions.