If you are reasonably fast on your commute and get out on the road you will be amazed at what kind of speed you can maintain when you aren't having to stop/start/stop/start as long as the conditions are nice.

I ride to see my mom who lives 75km away and once I get out of the city I can maintain 30kmh on my touring bike with a light load... the route is about as flat as one could imagine... unless you live in Florida. Getting out of the city takes about an hour as it is 20km from my home to the highway but once the road opens up you can maintain a really nice pace.