Field Test / Fitness Test

Today was my fitness test day. 3 miles on the bike as fast as I can go. 10 min. recovery and do it again. 8:07, 180 avg HR, 22.3 avg mph. It seems like I should be able to go faster than that. I have before after 2 hours of riding, fighting in a group ride. Maybe that's better motivation for me. It was cold out and I feel stronger after about an hour of riding, not a 20 min warm up. However, the conditions were similar the last time I did this, my avg HR was higher but I was faster this time, so that means I'm doing something right? I need read up on this some more. I do this at Columns Drive near 400 and Powers Ferry. The road is mostly flat, 2.5 miles long so I have to do a 180 to finish the 3 mile course.