The route can have a big influence on average speed.
Are there traffic lights? Is it windy? Is the road smooth or rough? And most significantly: How much vertical gain/loss on the route?
My rides are averaging 14-17 mph, and I'm considered a fairly fast 64-year old. But I don't pay attention to average speed.
Average speed is not a good measure of effort. If you want a good measure, get a power meter. I use the
Favero Assioma single-sided pedal power meter.
