FYI, the Philly Naked Bike ride is this weekend (and the weather's looking nice)
Bicycle safety and infrastructure is one of the causes they ride to promote (as well as body positivity, and reducing carbon emissions)
It's also just a silly fun time, I did it last year and would be there again this year if I didn't have another obligation, I'll be there again next year hopefully.
They announce the route about 24 hours before the ride, it's usually around 12 miles and they keep the pace pretty slow. I'm about as casual of a cyclist as they come and I didn't have trouble keeping up.
It's "bare as you dare" if you don't want to get naked for it. Plenty of people ride in underwear, bathing suits, wacky costumes, or just clothing. I wore some goofy leopard print underwear myself (I'm plenty comfortable being naked but I don't need pictures of my dick posted around online.)
It's also open to other forms of people-powered transportation if you'd rather skateboard, rollerblade, ride a scooter, or jog it.
It gave me a great appreciation for how bike-friendly Philly could be, most of the city is pretty flat, not a whole lot of hills to kill yourself going up, but unless I'm riding in a pack of hundreds of people or if we could get some more parking protected bike lanes, I just don't feel safe riding around most of the city.