Your question can be closely answered by using the Garmin data from my 305. Once I download the data after a ride onto my desktop Garmin software, it gives me the time spent on each 1 mile lap. Now, I could have set the lap distance to something less like a half mile per lap. That might make it more finite.

I go on Excel and construct the formulas to calculate the average speed after removing the slowest laps. Suppose I go on a 20 mile ride and 2.5 of those lap miles were the slowest. Then I know that 12.5% of that ride can be removed to arrive at an adjusted average.

That way, I can isolate the average speed to the warm up miles and the riding in stop and go traffic, and the long climbs.

The Garmin software also allows me to see the route on Google Earth. That is, the actual ride is mapped out.