The appeal is dismissed.

The costs of appeal are assessed against the plaintiff (Counterclaim defendant).

The grounds of appeal are examined.

1. As to the grounds of appeal Nos. 1 and 2

A. The illegality as a requisite for establishing a tort is not to be determined by all relevant acts, but to be determined individually and indirectly by each act at issue. Thus, in a case where a third party is damaged due to harmful emission generated from a facility lawfully operated or provided for public use, its illegality should be separately determined.

In such cases, the standard of judgment is whether the degree of harm exceeds the degree that it should generally be identified by social norms (hereinafter referred to as "limit of participation").

(see Supreme Court Decision 9Da55434, Feb. 9, 2001). A person who installs, manages, and manages an expressway is liable to compensate for any damage caused by any defect in the installation, maintenance, and management of the expressway, pursuant to Article 758(1) of the Civil Act.

Defect in installation or preservation of a structure means that the relevant structure is in a state of insufficient safety to be equipped for its intended purpose.

Here, the state of non-safety, i.e., the state of danger that may cause harm to others includes not only physical or external defects or the lack of necessary physical facilities in itself, but also the state of causing damage exceeding the limit of participation by social norms to third parties in the course of using the structure for its original purpose, as well as to the risk of harm to users because it does not have physical or external defects or necessary physical facilities.

In such cases, the nature and degree of damage, the public nature of damage interest, the type and mode of harmful act, the public nature of harmful act, the prevention measures against the perpetrator or the possibility of avoiding damage, the land violates the regulation standards in public law.