In response to a request from Shaney in a comment on a post about the Ken-oh-dou, I made a kmz file for Google Earth about an empirically-determined faster route from Tsukuba to Narita Airport.
My experience shows that this route has less traffic and fewer signals and it is easier to speed. It takes approximately 45-60 minutes to get to Narita on this route.
You can enjoy a tour of the route by clicking on “Tools” > “Play tour”.
The trick is to minimize your time on Route 408 as much as possible. The above route follows Route 408 after entering Chiba Prefecture, but I believe this part can be improved. Once I encountered a very slow, huge trailer three cars ahead of me carrying a very big part of something. It almost made me late for my flight that time.
I welcome other recommendations, impressions, and feedback. Let’s develop a faster route to Narita!