Here are some experiences shared in November '06 by riders who biked through the downtown-to-Sellwood section after dark.
http://bikeportland.org/forum/showthread.php?t=598
Also, this topic brought an idea to mind. I live in Sellwood and I wanted to participate in the bike rides in memory of Tracy and Brett but didn't because I would have been riding home alone in the dark either through the isolated, unlit, 3-mile long stretch of the trail between Ross Island Sand & Gravel and Sellwood or else on very undesirable streets. In the future, when there are evening bicycle events (hopefully for happier reasons), it would be nice if people in different neighborhoods could organize to ride home together after dark. Or maybe there already is a place where arrangements such as this can be made and I'm not aware of it. Like it or not, the Springwater Trail after dark reveals an arena of modern life where men have a bit more freedom than women.