The correct answer is Broad gauge.

• The Konkan Railway:
  • The Konkan Railway was the missing link between India’s commercial capital, Mumbai, and Mangalore.
  • The 741-kilometer line connects Maharashtra, Goa, and Karnataka States.
  • The railway is operated by the Konkan Railway Corporation, its headquarters at Belapur in Navi Mumbai.
  • The first passenger train ran on Konkan railway tracks on 20 March 1993, between Udupi and Mangalore.
  • The first train on the completed track was flagged off on January 26, 1998, on Republic Day.
  • The track gauge of the Konkan railway is the broad gauge (1,676 mm).

• Rail gauge:
  • The clear horizontal distance between the inner sides of two tracks is called a railway gauge.
  • Approximately sixty percent of the world's railway uses a standard gauge of 1,435 mm.
  • There are 4 types of railway gauges used in India-  Broad gauge, Metre Gauge, Narrow gauge, and Standard gauge (for Delhi Metro).
• Broad gauge:
  • Broad gauge is also called wide gauge or large line.
  • The distance between the two tracks in these railway gauges is 1676 mm (5 ft 6 in).
  • Any gauge, wider than standard gauge or 1,435 mm (4 ft 8½ inches), is called broad gauge.
• Standard Gauge:
  • The distance between the two tracks in this railway gauge is 1435 mm (4 ft 8½ in).
  • In India, standard gauge is used only for urban rail transit systems like Metro, Monorail, and Tram.
• Metre Gauge:
  • The distance between the two tracks is 1,000 mm (3 ft 3 3/8 in).
  • The meter gauge lines were made to reduce the cost.
• Narrow Gauge:
  • The small gauge is called a Narrow gauge or a small line.
  • The narrow-gauge railway is the railway track, in which the distance between two tracks is 2 ft 6 in (762 mm).