This weekend saw the launch of the sixth annual World Naked Bike Ride, in which... well, I guess it's pretty self-explanatory: Naked people on bikes will be riding through towns all over the world. And as I'm sure you have already guessed, they'll be doing it to raise, um, awareness of sustainable transportation solutions. And to drive home the point that there is no sustainability topic that can't be impoved by adding nudity.

This first portion covers cities across the Southern Hemisphere - where it's already almost autumn. The Northern Hemisphere gets a better deal (from a naked rider's perspective, anyway) with its events in balmy June.

But what's this? Of the dozens of cities on the itinerary, Philadelphia is so far not listed as a Naked Bike Ride participant! How can the City of Brotherly Love not have naked bikers when other, less "love"-based jurisdictions are flaunting them?

I asked Alex Doty, Executive Director of the Bicycle Coalition of Greater Philadelphia, what was going on and whether his group had a problem with naked bikers. Far from it, he said. "In fact, I think we should do the World ride one better in June and have the entire Bike Race go on naked." Doty did not explain how, in such a scenario, race announcers and commentators - or indeed, the riders themselves - would identify the members of different teams.

More seriously, though, Doty pointed out that rather than focusing on a one-day splash, the Coalition in May ("Bike Month")  is launching a program with the same goal of educating the public about bicycle options as well as bike safety, with an initiative called Bicycle Ambassadors. Throughout the summer they'll be appearing at events and sometimes right on the street to answer questions and gently prod the public bikeward.

But will any of the Ambassadors be naked? Doty allowed that he had not asked the question of any applicants so far and it did seem unlikely. "But I will promise you," he added, "that our Ambassadors will gladly talk to people who are naked. We will issue them special sunglasses for that purpose."