This spot is located on the Lyon-Genève line that was electrified in 1.5KV DC in 1956. For various reasons, mostly related to simplification and costs, the Bellegarde to Genève part of the line has just been re-electrified in 25KV 50Hz. The voltage change occurred in August and the works are not yet fully over. Right after Bellegarde in the direction of Genève, there is a 4km-long tunnel - the “Cret d’Eau” Tunnel - that has always been a problem because of its wetness, instability and constant presence of water. When changing for 25KV AC, it was decided to install an overhead rail instead of a catenary in the tunnel.
The picture shows the tracks right after the East portal of the tunnel. This is a junction between the line to Genève and the line to Annemasse. For a short distance and over the junction, the catenary is still the same overhead rail as in the tunnel, so that the connection with a standard catenary can take place where the track ride is smoother than over a curve and switches (right over the photographer). As a consequence, a maze of overhead rails hangs over these switches. This stuff is heavy and requires many more poles than a standard catenary. The result is this incredible ceiling of 25 thousand volts apparatus. The telephoto lens makes this installation look even more intriguing.