You Europeans can afford to be a bit more relaxed about events like the World Naked Bike Ride than those of us in the US.
At least in places like England and Wales, public nudity is not against the law so there isn’t the danger that you can be arrested and charged just for being nude in one of these protest rides.
In the US there are various public nudity and indecent exposure laws on the books, and in some cases the local police may conveniently overlook them for events like this, but there is always the danger that situation could change on a moments notice and with a citizen complaint.
It is possible that you could be charged with being a sex offender and have to register your residence with local authorities and notify your neighbors of that status for the rest of your life.
The WNBR in New York is not given an official permit, and riders have to leave their staging area in groups smaller than a legal size limit, and the police will stop and could arrest any riders whom they see exposing their “private” parts.
Both the biggest ride in Portland Oregon and the ride in Chicago are held at night in the middle of a weekend to avoid having other people on the street, and limiting the amount of quality photos and videos that can be taken.
In Philadelphia, the ride is delayed until September and run on a Sunday evening in the middle of a three day national holiday weekend and over a four mile course in the deserted downtown area.
If you look at the participants in these rides they appear to be mostly under 30 years of age, and they are the types of young folks who have jobs with limited futures like waitressing in a coffee shop, working in a book store, or some other low pay no growth occupation.
By contrast, if you observe the riders in London, they span all age groups, and you may find some very middle class looking married folk of middle age and even some senior citizens.
In the states, having your nude picture posted on the Internet can cost you your job or your career and pension if you are a public employee like a school teacher, or it can cost you your job and any future promotions if you are employed by large corporations. This is true even if the picture is taken without your permission in a perfectly legal nude setting like the federally owned and operated Gunnison Beach in New Jersey. An otherwise innocent day at the beach can literally ruin your life without you knowing the picture is being taken and will later be posted for all the world to see and copy long term.
So, riding nude in one of these local parts of the WNBR demonstrations is really inviting potential problems since the rides are designed to attract publicity to an environmental cause and the way to get that attention is to have as many pictures and videos taken as possible and have them as widely distributed as possible. A photograph taken in a half second could live forever kicking around the Internet and cause the subject embarrassment and ridicule in their personal lives for years to come.
If that isn’t quite the case in Europe, than the whole European society is more relaxed about the nudity, but something tells me that is not necessarily true in the Catholic countries in particular. On the other hand, Scandinavia, the Netherlands, and the UK are a little more relaxed than the US, and I think Canada and Australia may be too.