I parked my car in the supermarket parking lot. When I returned I noticed that there was a lot of glass under my parked car. Apparently, while I was in the supermarket someone dropped a few bottles and the broken glass bottles rolled or were pushed under my car. If I drive away carefully I will avoid damage to my car but I will expose the broken glass and another car can have his tires damaged by driving over the glass. Must I clean up the glass before leaving or am I not responsible since I didn’t put the glass there?
A case in the Gemoro is quite similar to your situation. The Gemoro (Bava Kama 30A) says that if someone stored his glass in another person’s wall and one day the owner of the wall demolished the wall causing the glass to fall onto public property, the owner of the glass is responsible for any ensuing damages. The Gemoro says that this ruling applies only to a fragile wall where one could expect that the wall would fall or be demolished soon. This is quite similar to your situation where it was to be expected that you would drive away.
The possible issue in your case is that you knew that there is glass under your car, whereas in the case of the Gemoro it is not clear that the owner of the wall knew that there was glass hidden in the wall.
The issue whether the ruling of the Gemoro would change if the owner of the wall had noticed that there was glass in the wall before demolishing the wall, is the subject of a dispute amongst the Rishonim. The Nemukei Yosef (Bava Kama 14A) explains that the reason the Gemoro ruled that the owner of the wall is not responsible is because he need not suspect that someone hid glass in his wall. The implication is that if the owner knew that glass was hidden in the wall, he would be responsible.
This is disputed by the Tosafos Rid who explicitly writes that the owner of the wall isn’t liable because he has the right to demolish his wall and he has no responsibility for objects that were placed in his wall. Besides the Tosafos Rid who is explicit, the Divrei Yecheskel (siman 50) proves that Rashi and Tosafos agree with the Tosafos Rid.
The Chazon Ish (Bava Kama 2, 20) without citing any Rishon, rules like the Nemukei Yosef. His rationale is that even though the one who placed the glass in the wall acted improperly, that does not license the owner of the wall to dump the glass into the public domain, because the public doesn’t have to suffer the consequences of the glass owner’s misbehavior. Therefore, if the owner of the wall noticed that there was glass in his wall and yet he nevertheless proceeded to demolish the wall causing the glass to land into the public domain, the owner of the wall is liable.
Based on what we learned in the previous paragraph it would seem that the answer to your question is that it is a dispute among the Rishonim.
However, one can differentiate between your case and the case of the wall. The difference is that in the case of the wall, as long as the wall remained intact there was no glass in the public domain. Only when the wall was demolished did the glass enter public property. Therefore, if one noticed the glass he is responsible if he caused the glass to enter into the public domain according to the opinions previously cited. However, in your case the glass was in the public domain even when your car covered it. Your car was being used as a cover for a bor which was already sitting in the public domain. Therefore, your situation is most similar to one who took someone else’s board to cover his pit, where the Gemoro (Bava Kama 30A) rules that the owner of the board may remove his board and liability remains exclusively with the one who dug the pit.
Proof of the above distinction can be brought from the Chazon Ish (ibid). As we mentioned, the Chazon Ish maintains that if the owner of the wall noticed the glass in the wall before demolishing it, he is responsible for damages suffered by others from the fallen glass. Nonetheless, he writes that if the glass was originally situated next to the wall so that people would not suffer damage from the glass because they do not walk right next to the wall, and then the owner of the wall demolished his wall leaving the glass where it was but now exposed, the owner of the wall is not responsible for the ensuing damages. The rationale is as we explained. Therefore, you may drive away without concern.
Finally, whether the original owner of the glass will be responsible for damages depends on the cause of the glass breaking. If it broke because the original owner was careless, he will be responsible. However if it resulted from circumstances out of the original owner’s control and he immediately relinquished ownership he too will not be liable.
he too will not be liable.