I’ve checked my speeds against Google maps and they use around 19Kph for calculating times. This is very reasonable considering that many of us commute in urban settings. I don’t know about you, but I tend to time the lights so I’m always riding on green. Depending on” line of sight” conditions, this allows me to conserve my momentum. Grade can affect this as well. A drop of 4 or 5 feet over a mile can reduce rolling resistance, considerably, and make for a sweet ride without breaking a sweat. These postings are great and give me food for thought when calculating traffic volume issues. Now, if someone can design a bike route that goes downhill both ways, you’re on to something. Come to think about it, when you consider the amount of earth they move making roadways for motorized vehicles, designing a roadway with a 4 or 5 foot drop would be cheap and very encouraging for “low wattage” riders.