Health and Safety, French Style:
To put this in context, this is a pontoon for leisure boats about 500m from the city centre. The nearest passenger walkways are some distance away. This makes the metal boom a very desirable way for the legitimate and not-so-legitimate to access the pontoon.
Just imagine the barbed wire, land mines and warning signs if this were in the UK.
One of the great things about being in France is the noticeable absence of 'thou shalt not' signs.
"Thou mayest do as thou pleasest, but if thou comes a cropper, thou hast only thyself to blame."