India's first Bengaluru–Hosur Interstate Metro Corridor declared Technically Infeasible

Bengaluru, India (Metro Rail Today): The ambitious plan to connect Bengaluru and Hosur through South India’s first interstate metro line has reportedly hit a roadblock, with the Bangalore Metro Rail Corporation Limited (BMRCL) declaring the project “technically not feasible.”

According to officials, the primary challenge stems from differences in traction systems between the two proposed metro networks, making integration impractical despite the project’s strategic potential.

While the Tamil Nadu government has strongly supported the Hosur–Bommasandra corridor as a means to boost industrial and economic growth in Hosur, BMRCL engineers say technical incompatibility has rendered the project unviable for seamless operation.

The feasibility study conducted by Chennai Metro Rail Limited (CMRL) proposed a 25 kV AC overhead traction system for the Hosur–Bommasandra line. However, Bengaluru’s Namma Metro operates on a 750 V DC third rail system, which is incompatible with CMRL’s high-voltage AC configuration.

“Building a continuous line from Bommasandra to Hosur is not technically feasible. The Hosur line just cannot be integrated into our system,” a senior BMRCL official told Deccan Herald, confirming that the corporation has shared its assessment with the Karnataka government for final consideration.

BMRCL had also evaluated an 11-km extension from Bommasandra to Attibele, the last major suburb before the Tamil Nadu border, under its existing DC system. However, the proposed Hosur line beyond Attibele would require a switch to the AC traction system, making through-running of trains impossible without a complex and costly power interface.

Metro Expansion Back on Track Within Karnataka

Even as the interstate link appears uncertain, BMRCL has accelerated its metro expansion plans across Karnataka. The agency is currently finalizing feasibility reports for four new extensions and conducting studies for three more, alongside one entirely new corridor.

Ongoing projects under the proposed Phase 4 include:

• Bommasandra–Attibele (11 km) – 7 to 8 stations.

• Green Line extension (Madavara–Tumakuru, 59.6 km) – 25 stations; estimated cost ₹20,896 crore.

• Southern Green Line (Silk Institute–Harohalli, 24 km) – 18 stations.

• Purple Line extension (Challaghatta–Bidadi, 15 km) – 13 stations.

Feasibility reports for all four have been prepared by Aarvee Associates Architects Engineers and Consultants Pvt. Ltd., with final submissions expected by October-end.

470-km Master Plan to Transform Bengaluru’s Mobility

In line with directions from the Ministry of Housing and Urban Affairs (MoHUA), BMRCL is preparing a comprehensive metro master plan to expand the city’s network to 470 km, placing Bengaluru almost on par with Delhi-NCR’s 467 km metro system.

The plan includes three new extensions and one new line:

• Blue Line (Doddajala–Devanahalli, 10 km)

• Purple Line (KR Puram–Hoskote, 16.3 km)

• Silver Line (Kadabagere–Tavarekere, 6 km)

• New 68-km corridor (Kalena Agrahara–Kadugodi Tree Park) via Bannerghatta, Jigani, Attibele, Sarjapur, Dommasandra, and Varthur Kodi.

Together, these additions will expand Namma Metro’s total planned network to 467.69 km, marking one of India’s most extensive metro expansion drives.

“Preparing a single master plan will help us avoid piecemeal approvals and fast-track development,” said a senior BMRCL official. “The focus now is on large-scale, interconnected corridors exceeding 200 km to effectively tackle Bengaluru’s traffic crisis.”

Mrs. Mamta Shah, MD & CEO, Urban Infra Group, underscored the importance of harmonizing metro technologies across Indian states to enable future interconnectivity:

“The Bengaluru–Hosur corridor could have been a landmark in interstate metro integration, but this setback highlights a broader issue — the lack of standardization in traction and signalling systems across India’s urban rail projects. As India builds its next generation of metro networks, establishing unified technical standards will be crucial to achieving long-term interoperability, cost efficiency, and scalability under the Viksit Bharat 2047 vision.”

While the interstate metro dream may have dimmed for now, BMRCL’s renewed focus on internal expansion marks a decisive move toward building a world-class, citywide urban transport system.
If executed as planned, Bengaluru will soon boast one of the largest and most advanced metro networks in the country — redefining urban mobility for millions of commuters.