Riding the waves of the oceans of the world sounds reasonable enough. However, riding the exteriors of New York City subway cars defies a reasonable exercising of judgement.
The prominently placed signs (as pictured) can be seen while riding in many NYC subway cars. Inquisitive by nature, I questioned the legitimacy of the ads. As it turns out, several years ago someone died 'surfing' the subway.
It is no one's place to judge the actions of others. Although I am confident you will not find me 'riding the rails' in this manner anytime soon, I do have one lingering thought: why are these signs placed on the interiors of the subway cars? How do they anticipate reaching their target audience if they are 'surfing' on the outside of the car?
Whatever the case the message is simple: "Ride inside. Get there alive."