This is probably an interesting story but we're just lazy linking to Wikipedia here and Wikipedia has no details. Why was it considered impossible to build this road? All we have is construction details in two to three paragraphs
The OP could've done more to explain it, but it really is a fascinating subject. Saba is an extremely steep island which, for most of its history, had no point of access except for a set of 800 stone stairs called "the ladder". everything brought to the island had to be carried up the ladder on foot, including large items of furniture. Given this, construction equipment wasn't an option.