Just because cable cars offer wonderful nature views, doesn't mean they should offer views of folks getting down au naturel.
The cable car service in China's Yaoshan mountain is supposedly safe, but bumping and grinding might cause the cable car to start-a-rockin'. That seems far less safe.
It's not just shaking cable cars that led to the sign. The cable cars pass each other on their way up and down, and after a couple was filmed having intercourse in one, a sign was erected where visitors board the cable cars to prohibit them from erecting other things in the cable cars.