The decision to build a new railway alignment deep beneath the ground in the narrow Siliguri Corridor, popularly known as the Chicken’s Neck, reflects a strategic shift in how India is hardening its most critical transport links. The corridor is the country’s only land bridge connecting the northeastern states with the rest of India and, at its narrowest point, is barely a few tens of kilometres wide. It carries a dense web of highways, rail lines, pipelines and communication networks, all of which are essential for civilian mobility, commercial supply chains and military logistics. Any prolonged disruption in this stretch would have immediate and far-reaching consequences for both national security and the regional economy.
Against this backdrop, Indian Railways and defence planners have concluded that surface-level expansion alone is no longer sufficient. While additional tracks are being laid on the ground to raise capacity, two new railway lines are planned well below the surface, at depths that place them beyond easy detection or damage. The primary objective is to ensure that rail connectivity between mainland India and the Northeast remains functional even in extreme scenarios, including hostile action, sabotage or precision strikes. Underground lines are inherently harder to target, more difficult to disable quickly and easier to protect through controlled access points and monitoring systems.
The depth of the alignment is also tied to survivability. The alignment is planned at a depth of around 20 to 24 metres below ground level, placing the tracks beyond easy detection and reducing vulnerability to surface-level threats or blast impact. This depth is intended to ensure that rail operations can continue even under extreme or hostile conditions.
Shallow cut-and-cover tunnels or partially buried tracks would still be vulnerable to modern weapons, heavy aerial bombardment or drone-based attacks. A deeper tunnel profile offers greater protection from blast effects and ground shock, improving the chances that trains can continue operating or be restored rapidly if surface infrastructure is compromised. For military logistics, this translates into a secure artery capable of moving troops, equipment and supplies without dependence on a single exposed route.
Operational resilience is another key driver. The Siliguri Corridor already handles heavy passenger and freight traffic, and demand is expected to rise as economic activity in the Northeast expands. By combining surface lines with underground ones, planners are creating multiple parallel paths for trains. This layered network provides redundancy, meaning that even if landslides, floods, accidents or security incidents affect one section, traffic can be diverted to alternative tracks. The underground alignment therefore complements, rather than replaces, surface expansion, together forming a more robust transport system.
Geography further explains why the project is being treated with exceptional importance. The corridor sits close to several international borders and near sensitive regions where geopolitical tensions have periodically flared. Infrastructure in this area has long been viewed through a strategic lens, not only as a development asset but also as a potential vulnerability. By placing a portion of the railway network underground, India is effectively insulating a critical lifeline from the risks associated with its exposed location.
There are also long-term planning considerations. Building deep tunnels now is more expensive and technically demanding than adding surface tracks, but it reduces future costs associated with repeated repairs, security upgrades and emergency responses. Over the lifespan of the infrastructure, a hardened underground corridor is expected to deliver greater reliability and lower disruption risks, which is especially important for a region where alternative routes are limited.
In essence, the depth of the railway line at the Chicken’s Neck is not an engineering flourish but a strategic necessity. It is intended to transform a historically vulnerable stretch into a resilient, multi-layered transport corridor capable of withstanding both natural and man-made shocks. By doing so, India is seeking to secure uninterrupted connectivity to its northeastern states, strengthen national defence preparedness and support sustained economic integration of the region with the rest of the country.