Having a speedometer on the bike helps me get a better workout by letting me compare how fast I come past various landmarks -- this is better than seeing what *time* I get to those landmarks because it lets me ignore the effect of traffic lights. One of my landmarks is the minuteman statue in Lexington, which I like to pass going at least 20 mph. This morning I passed it at 23 mph, and at the same time also passed another cyclist who was doing about 20. He chased me down and drafted me to the end of the bikepath at which point I convinced him to follow me up Springs Road and do some intervals. Wow, having someone else along on those made me work a lot harder. He did well, too, especially on the longer ones, and came past the high point of Springs Road half a bike length ahead of me. We rested a bit more between the intervals than I usually do so I don't know if it was any faster than usual but it sure left me more sore.