Four SK lines were built in Paris metropolitan during the 1990's but only one was opened to passengers and it is not anymore in service.
One line was built to in the car park of the Villepinte Exhibition center.
It was rather useless, it wasn't so much faster than walking.
Two lines were built to serves CDG airports, the two lines were almost fully completed but the line 1 had serious technical issues and the second while working well has not been not opened.
The infrasctructure oif the first line of CDG was reused for the driverless
CDGVAL line 1.
One line was constructed in Noisy-le-Grand (eastern suburbs).
This line was built to link the RER station and the mall of Noisy le Grand Mont d'Est with an housing complex called Mail-Horizons.
This complex was never built due to the bankruptcy of the developer.
As the area of the project where is located the second station is a wasteland, the line has never been opened.