smallgauge

Smallgauge is a term used to describe railway systems that operate on gauges narrower than the standard gauge of 1435 mm (4 ft 8 1/2 in). In practice, the label is not universally defined and overlaps with the broader concept of narrow gauge. Different regions and sources may apply the term to a range of gauges from around several hundred millimeters up to the meter gauge category (1000 mm).

Historically, narrow and small gauges arose to reduce construction costs, allow tighter curves, and permit operation in difficult terrain or confined sites such as mines, plantations, and mountainous regions. Lighter rolling stock, simpler track structure, and lower speed requirements characterized many smallgauge lines. As rail networks expanded globally, engineers often chose smaller gauges for feasibility rather than standardization, resulting in a diverse spectrum of regional gauges.

Common uses of smallgauge systems include industrial transportation within mines and forests, short-haul or branch lines in rugged areas, and heritage or tourist railways where space and budget constraints favor compact gauges. In addition, garden railways and certain hobbyist or model railroad contexts reference smallgauge concepts when discussing scales and track widths for miniature or outdoor layouts.

Today, smallgauge remains relevant in historical studies of rail technology, in discussions of industrial logistics, and in the preservation and operation of heritage lines. It also informs design choices for new installations in constrained environments, where a smaller gauge can enable access and cost savings while delivering functional railway service.

See also: gauge (railways), narrow gauge, standard gauge, industrial railway, heritage railway.