On the way home from the grocery store on Tuesday, with a bike weighed down with 30lbs of groceries, I kept it to an easy 12-15mph. I noticed that at this speed, drivers were safer when passing me, and I didn't have as many conflicts with them (ie, right hooks).
My experiment: I would like a few people to join me in an experiment. We will alternate days when we actively stay at a slower pace of 12-15mph and when we ride at the speed we desire. For me, that's normally between 17-20mph. It might be slower for you. I want to do a quasi-experimental evaluation of how cycling speed might affect your ride and interaction with motorists. I invite you to make your own speculation on why certain speeds incur certain results. This is definitely a subjective test, but I want to see if anyone else experiences the things I do.
So how bout it? Any volunteers? Email me at firstname.lastname@example.org for details on information. (And it's totally okay if you don't live in LA.)