Originally Posted by carpediemracing

What some of the folks are trying to say is that average speed is simply one measurement of how you're doing.

In order to improve average speed, you need to mix up your riding. For example, if you want to do a heavier bench press, you don't do your max bench every day. You do some other structured thing (pyramid or lighter weights and higher reps or whatever). Then after some specific training, or in the case of benching, simple recovery, you try your max again.

Likewise, in cycling, if you are constantly focused on your average, you'll be missing out on the training you need to go faster, be more fit, etc. Average is like doing the exact same workout every day. Although you'll eventually improve there are much better ways to go about it.

You may do one ride where you sprint for 10-15 seconds every time you get to one of those underpasses. Your average speed will probably suffer, it'll make you sore, but after a day or two, once you recover, you should be marginally stronger. Multiply this over a few weeks or months and you may find that your overall average is now 17 mph instead of 15 mph.

You're at the speed where increases plateau - this is because air resistance increases exponentially. At around 17-19 mph it becomes substantially more difficult to increase average speed.

The best way to increase average speed, your overall cycling ability, and add an element of errr unpredictability to your riding is to do group rides. Find a shop or a club or a list of rides and look at joining ones that, at first, claim to average 15 mph. Then work your way up to faster rides. I think you'll find the incredible assortment of riders, equipment, ability, and etiquette to be astounding. And your riding will improve exponentially, I guarantee it.

Group riding will pressure you to perform on the bike in a way that solo riding simply cannot accomplish. Racing is one step beyond that, if you so desire. Either of them will significantly and immediately improve your speed, and you've probably figured out that the speed is the key. If your outward leg was 23 mph, your overall avg would go up. If you returned at, say, 15-17 mph, you'd be looking at a 17-18 mph average. Speed is the key to this particular game (avg speed) and the best way to improve is to ride with others who are, at least for the moment, faster than you.

hope this helps and good luck with improving your average speed,
cdr