Doug Westly's Safety Talk about merging is a winner. It also helps to have the occasional car driver cut you some slack.
Last night I was merging onto a section of interstate that runs as close to West-to-East as you'd ever find. And while there isn't a LOT of rise and fall, it also isn't flat. I was merging onto the road with the sun directly at my back. 20 minutes or less later and the sun would have been below the horizon. And we were on a slight downslope...just enough that the sun was absolutely BLINDING behind me. I picked a spot, flipped on the turn signal, stuck my arm out for a hand signal, accelerated, glanced in my mirror, and after seeing a hint of a car, I was immediately and completely blinded by the sun. I cranked my head around to look over my shoulder only to find that was no better than the mirror...the outline of a car and SUN. I knew I'd be running out of acceleration ramp soon, but decided to hunker down a bit to see if I could see anything through just the very edge of the mirror (thank goodness for my vintage bike with mirrors on nice long stalks). The car must have seen my predicament and was more "cycle aware" than most. Through just the edge of the mirror, I could see he was no longer closing on me. I was able to merge into the traffic flow and then quickly regain whatever speed necessary to match the surrounding traffic.
I was grateful for a car driver who gave me a little space and gave him a big wave as I moved on.