High Density Network (HDN) is a group of seven high density railway corridors of the Indian Railways. Together, these corridors account for approximately 16 percent of the total route length of the Indian Railways but handle about 41 percent of its combined rail traffic.

Overview Indian Railways has classified seven high density railway corridors as the High Density Network (HDN). These corridors span , connecting the major cities of Chennai, Delhi, Guwahati, Kolkata, and Mumbai. The HDN corridors account for approximately 16 percent of the total route length of the Indian Railways but handle about 41 percent of its combined rail traffic. Along with the Highly Utilised Network, which covers a further , these networks carry an estimated 96% of the total traffic of the Indian Railways while accounting for about half of its total route length.

Corridors

+List of corridorsName Corridor Zone(s) Major stations Route length (km) Single line Double line Triple line Quadruple line Penta/Hexa line Total HDN-1 Delhi–Howrah NCR, ECR, ER Dankuni Jn., Asansol Jn., Dhanbad Jn., Prayagraj Jn., Kanpur Central 948.00 280.75 186.61 6.57 1,421.93 HDN-2 Howrah–Mumbai CR, SECR, SER Kharagpur Jn., Tatanagar Jn., Jharsuguda Jn., Bilaspur Jn., Nagpur Jn., Bhusaval Jn., Igatpuri 1,123.10 704.00 211.67 2,038.77 HDN-3 Mumbai–Delhi NCR, WCR, WR Surat, Godhra Jn., Ratlam Jn., Nagda Jn., Sawai Madhopur Jn., Mathura Jn. 1,176.64 4.01 125.91 13.97 1,320.53 HDN-4 Delhi–Guwahati NR, NER, ECR, NFR Moradabad, Roza Jn., Gonda Jn., Gorakhpur Jn., Katihar Jn., New Jalpaiguri Jn., Rangiya Jn. 250.32 1,612.26 12.34 1,874.92 HDN-5 Delhi–Chennai NR, NCR, WCR, CR, SCR Mathura Jn., Jhansi Jn., Bina Jn., Bhopal Jn., Nagpur Jn., Balharshah Jn., Vijayawada Jn. 1,120.97 899.53 17.95 2.22 2,040.67 HDN-6 Chennai–Howrah ER, SER, ECoR, SCR Kharagpur Jn., Bhadrak, Visakhapatnam Jn., Vijayawada Jn. 988.85 111.00 17.00 1,116.85 HDN-7 Mumbai–Chennai CR, SCR, SR Pune Jn., Solapur, Guntakal Jn., Arakkonam Jn. 1,143.30 28.00 66.26 1,237.56 Total 250.32 8,113.12 2,039.63 625.40 22.76 11,051.23

Utilisation The concentration of traffic has resulted in significant capacity constraints across the HDN. According to the Indian Railway Board data as of December 2024, only 4.6% of HDN route-km operated below 80% of charted line capacity, while approximately 44% operated above 120%, indicating substantial saturation on many sections. Certain sections experience severe congestion such as the Karjat–Lonavala section of the Mumbai–Chennai line, which has been reported to operate at more than 167 percent of charted capacity.

+Utilisation of HDN Utilisation band Route length (km) Share of HDN Less than 80% 518.9 4.6% 80–100% 2,088.0 18.89% 100–120% 3,619.0 32.75% 120–150% 3,263.9 29.53% More than 150% 1,560.1 14.11%

Infrastructure Given their economic importance, Indian Railways has undertaken comprehensive capacity assessments and infrastructure upgrades such as track doubling and expansion, electrification, and the installation of automatic signalling systems. , Kavach, an indigenous automatic train protection system, has been commissioned across about 2,490 route-km on the Delhi–Mumbai and Delhi–Howrah corridors.

Mission Raftar is an initiative of the Indian Railways aimed at increasing permissible train speeds across the national railway network. Under the programme, selected HDN corridors, including the Delhi–Mumbai corridor, have been identified for infrastructure upgrades to enable speeds of up to . Dedicated Freight Corridors spanning more than are being constructed to enable faster freight movement while reducing freight traffic on existing HDN routes, thereby releasing capacity for passenger services. Indian Railways has also announced plans to quadruple the entire HDN network, creating four-line corridors to further increase capacity for passenger and freight operations.

See also Rail transport in India

References