A method for illuminating a tunnel of a highway.

摘要

A method for illuminating a spot inside a tunnel (30) of a highway by the use of a solar ray collecting device (10) which is to be used to focus a solar ray and guide it into an optical conductor (20). The solar ray transmitted through the optical conductor would illuminate an entrance portion of the tunnel and a light-emitting portion (40) of the optical conductor would disperse so as to gradually weaken the illumination inside the tunnel in accordance with an increase of distance between the entrance portion and a spot to be illuminated in an inner space of said tunnel.