Note: Minor stations omitted The New Delhi–Chennai main line is a railway line connecting Chennai and Delhi cutting across southern part of the Eastern Coastal Plains of India, the Eastern Ghats, the Deccan Plateau and the Yamuna valley.

[2] The Agra–Gwalior line was opened by the Maharaja of Gwalior in 1881 and it became the Scindia State Railway.

In 1889, the main line of the Nizam's Guaranteed State Railway was extended to Vijayawada, then known as Bezwada.

[7] New Delhi, Mathura Junction, Agra Cantt., Gwalior, Jhansi, Bhopal, Habibganj, Nagpur, Ramagundam, Warangal, Vijayawada, Gudur and Puratchi Thalaivar Dr. M.G.

The routes connecting the four major metropolises (New Delhi, Mumbai, Chennai and Kolkata), along with their diagonals, known as the diamond quadrilateral, carry about half the freight and nearly half the passenger traffic, although they form only 16 per cent of the length.