A motorist going 10 mph on a 30 mph speed limit street isn't breaking any law, neither is a cyclist. Driving slow on a single lane road is not impeding traffic anymore than red lights, yield signs, or left hand turns are impeding traffic.
http://www.nolo.com/legal-encyclopedia/free-books/beat-ticke...
"The law will excuse your slow driving if you can show:
You were driving slower than the posted speed, but lower speed was "necessary for safe operation" of your vehicle."
A motorist going 10 mph on a 30 mph speed limit street isn't breaking any law, neither is a cyclist. Driving slow on a single lane road is not impeding traffic anymore than red lights, yield signs, or left hand turns are impeding traffic.