IISc Flags Flaws in Bengaluru's Hebbal Tunnel DPR

IISc Study Challenges Tunnel Project

The Indian Institute of Science (IISc) has thrown a technical challenge at the proposed Hebbal Junction–Mekhri Circle tunnel in Bengaluru just as procurement nears award.

A study from the institute's Infrastructure and Sustainable Transportation (IST) Lab, led by civil engineering professor Ashish Verma, argues the project may not solve congestion and could cost roughly six times more than a Metro alternative per unit of passenger capacity.

The timing matters commercially. Adani Enterprises has emerged as the L1 bidder, but the contract remains pending.

An adverse technical review at this stage shifts the risk profile of an award the Bruhat Bengaluru Mahanagara Palike (BBMP) was expected to close.

The study's cost-per-passenger estimate of Rs 5.23 against Rs 0.86 for Metro — and Rs 13.74 lakh versus Rs 2.26 lakh per unit of capacity — undercuts the project's value-for-money case.

Technical Critique Targets DPR Assumptions

The critique goes beyond cost. The IISc team alleges the Detailed Project Report (DPR) used road-capacity figures inconsistent with the Indian Highway Capacity Manual, including lower capacities for the Hebbal flyover and upwardly revised baseline traffic numbers.

It also flags:

- A 60-metre-radius curve near the Esteem Mall exit that would force speeds down from 60 kmph to 40 kmph, creating queueing the DPR did not model.
- A low-lying tunnel entrance near Hebbal Lake that raises flood exposure during heavy rainfall.

Award and Governance Implications

For Adani Enterprises, the immediate issue is award certainty.

If BBMP is compelled to revise the DPR, revalidate traffic assumptions, or re-examine the Metro option, procurement could slip into redesign or re-tender.

That carries bid-cost, mobilisation and order-book timing implications for the contractor and its tunnel supply chain, including TBM and segment-casting commitments.

The deeper signal is governance. Independent academic scrutiny is now arriving after L1 selection, treating DPR assumptions as contestable rather than settled.

Bengaluru's congestion capital is being forced toward a higher burden of proof: a road tunnel must now justify itself against mass transit on capacity economics, not just engineering feasibility. That shift begins at Hebbal.