Bengaluru: In a major cost-optimisation move, the upcoming Phase 3A of Bengaluru’s Namma Metro, also known as the Red Line, will feature underground stations that are 40 metres shorter than originally planned. The decision comes after project authorities revised the total estimated cost downward by ₹2,920 crore, following a review directed by the Union Ministry of Housing and Urban Affairs (MoHUA).

Cost reduction after central review

The Karnataka Cabinet had approved the Detailed Project Report (DPR) for Phase 3A in December 2024, pegging the cost at ₹28,405 crore — or ₹776 crore per kilometre — making it the costliest metro phase yet. However, MoHUA found the estimate “significantly higher” than national benchmarks and asked the Bangalore Metro Rail Corporation Limited (BMRCL) to reassess the figures.

BMRCL then engaged French consultancy firm Systra to carry out a cost rationalisation study. Systra’s draft report, now under review by the ministry, identified tunnelling, station design, and electrical and mechanical (E&M) works as key areas where expenses could be reduced.

Underground station length reduced

According to the report, the original underground station length of 210 metres will now be cut to 170 metres, without compromising passenger capacity or operational efficiency. The platform length of 135 metres, required for six-coach trains, remains unchanged.

The reduction was achieved by reconfiguring non-essential operational rooms within stations. Some of Bengaluru’s existing underground metro stations are already about 190 metres long, demonstrating that shorter designs can function effectively.

Officials clarified that these changes would not alter the route alignment, system design, or passenger handling capacity.

Revised tunnelling costs and technical challenges

Tunnelling had been one of the biggest cost components in the original estimate. BMRCL initially pegged it at ₹300 crore per kilometre, while MoHUA’s benchmark for 2024 stood at ₹159 crore per kilometre. After review, Systra proposed revising the tunnelling cost to ₹210 crore per kilometre, considering Bengaluru’s unique geological challenges.

BMRCL officials explained that the city’s soil composition changes every 25–30 metres, making it impractical to apply uniform benchmarks across metro projects in India. “Bengaluru’s terrain requires frequent recalibration of Tunnel Boring Machines (TBMs), which adds to the cost,” one official said.

Phase 3A corridor details

The 36.59-kilometre Red Line will connect Sarjapur in the southeast to Hebbal in the north, passing through the Central Business District (CBD). The project includes:

  • An underground stretch from Koramangala 2nd Block through the CBD
  • A double-deck viaduct (metro-cum-road) from Sarjapur to Iblur (14 km) and Agara to Koramangala 3rd Block (2.45 km)
  • Seamless integration with existing metro lines and key arterial routes

The alignment closely follows the proposed Silk Board–Hebbal tunnel road project, with design adjustments near Hebbal to prevent conflicts.

Preliminary groundwork under way

While awaiting final approval from MoHUA, BMRCL has begun geotechnical investigations. In October 2025, tenders worth ₹6.86 crore were floated for soil testing across four project packages. Contractors are expected to complete the studies within 150 days once the contracts are awarded.

These studies will help determine soil strength, groundwater levels, and suitable tunnelling techniques — all critical for finalising engineering designs and selecting appropriate TBMs.

Completion timeline

Once the ministry clears Systra’s revised report, construction is expected to begin in 2026. The project is targeted for completion by 2031, aligning with Bengaluru’s broader urban mobility goals.

Officials believe that the cost optimisation exercise will ensure a more financially sustainable expansion without compromising service quality. “Phase 3A is designed to serve future commuter demand while maintaining global standards in efficiency and safety,” a BMRCL spokesperson said.