koninklijke
Draisine is the word for the ones used by service personnel; the word commonly used in Belgium, both by tourism sites and 'operators' is 'railbike' . 

Would consider adding the tag tourism=yes.

Thinking of English usage of the word preserved: If you preserve something, you take action to save it or protect it from damage or decay; also: when preserving a situation or condition, you make sure that it remains as it is, and does not change or end. Sounds just like what's done here?