Narrow-gauge railways in Canada

Although most railways of central and eastern Canada were initially built to a 5 ft 6 in (1,676 mm) broad gauge, there were several, especially in Atlantic Canada and Ontario, which were built as individual narrow-gauge lines. These were generally less expensive to build, but were more vulnerable to frost heaving because vertical displacement of one rail caused greater angular deflection of the narrower two-rail running surface.

Source: Wikipedia — Narrow-gauge railways in Canada (CC BY-SA 4.0)