I mainly ride in the City so that includes a lot of slowing and stopping. I average about 12-13 MPH on most of my rides. Many times if I see a red-light ahead I'll start slowing long before I reach it in the hopes it will turn green before my arrival..

On longer rides when I get outside the City my average ticks up a bit. Depends on how much of that was in the City and outside of the City..

I mainly just pay attention to my distance ridden daily, weekly, monthly, yearly and don't really care what my average speed ends up being.