My moving average that my computer tracks is pretty consistent near 15mph in the fall and spring. Little slower winter and in the summer heat.
Did a Metric last weekend on some pretty good rollers in the rain and moving average was 15.1 for the 62 miles. That's on a Touring bike with either panniers or a trunk bag. Moving time was something like 4 hours 15 minutes my total time out was about 5 hours 30 minutes