Shmuel and Rav Yochanan's position on how they understand the Mishna implies that if you actually see the vessel, you have to go around it. You can't break it deliberately. But if it's a bor in the middle of the street that can hurt other people, why can't I break it if I can help people from getting hurt?
Soheil Zaman, Sherman Oaks
I assume that this question is on 27b.
I saw on Otzar Hachochmah that the Mefarshim cite the Meiri on the Mishnah; that the person who placed the jug down in the street was tired and wanted to take a breather. It must be that in the short time that he was having a quick rest, somebody came and tripped up on it.
According to this we can say that one has the right to place down items in Reshut HaRabim for a short time if one is tired. The main street is also intended for travellers to take a short break, within reason. One is not allowed to break the property of a traveller behaving in this way.
Shabbat Shalom
Dovid Bloom