Dudelsack made a post in one of my threads that got me to thinking.

I don't want to post average speeds that are overinflated. If I had a nickel for every guy that posted he regularly hit 300 yard drives I would be rich man, or at least riding a carbon bike. So, how do you guys calculate your average speed?

For me I have Garmin eTrex Venture GPS mounted to my bike and I use the trip computer which calculates average speed based on time moving. In other words the time sitting at a stop light does not count against me. If I remember correctly my Cateye Cadence bike computer calculates the same way (I only use it for cadence since I have the GPS mounted to my bike).