Source: https://www.cevi.ch/depliants-reglements/?file=files/cevi/pdf/A-Franzoesisch/Depliants_Reglements/BFU/bfu_2.257.02_Documentation%20technique%202.257%20du%20bpa%20%E2%80%93%20Pistes%20et%20parcs%20de%20luge.pdf