Longman Dictionary of Contemporary English
light railway
noun
EXAMPLES FROM CORPUS
▪ If those words are retained in the legislation, those railways would still require a light railway order at some time.
▪ The company have retained the leisurely atmosphere of the turn-of-the-century light railway being situated off the major tourist circuits.
▪ The only other opportunity in the foreseeable future is likely to be the new light railway in London's Docklands.
Wiktionary
light railway
n. (context UK English) (alternative form of light rail English)
Wikipedia
Light railway
Light railway is a railway built at lower costs and to lower standards than typical "heavy rail"; it uses lighter-weight track, and is more steeply graded and tightly curved to avoid civil engineering costs. These lighter standards allow lower costs of operation, at the price of slower operating speeds and lower vehicle capacity.