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Hebbal tunnel won’t fix Bengaluru traffic, may lead to flooding: IISc report
An IISc study says Bengaluru’s proposed Hebbal tunnel may shift congestion to new choke points and cost over 6 times more than the metro.
The IISc Sustainable Transportation Lab study claimed that the traffic congestion will get shifted to new bottlenecks near the Veterinary Hospital and Esteem Mall. (File Photo)
An Indian Institute of Science (IISc) report has stated that the proposed short tunnel at Hebbal Junction in Bengaluru will not resolve congestion but relocate it to new choke points.
The IISc Sustainable Transportation (IST) Lab study, which was released on Tuesday, claimed that the traffic congestion will get shifted to new bottlenecks near the Veterinary Hospital and Esteem Mall, with spillover effects that could push queues back toward Mekhri Circle and effectively reduce the tunnel’s usefulness to zero over time.
Authored by Professor Ashish Verma of the Department of Civil Engineering of IISc, the study’s cost-benefit analysis found the underground metro to be far more economical on a per-passenger basis. Calculated by total passenger trips, the tunnel costs approximately Rs 5.23 per passenger compared to Rs 0.86 for the metro. Measured by passengers per hour per direction (PPHPD), the tunnel costs roughly Rs 13.74 lakh per unit of capacity versus Rs 2.26 lakh for the metro. By both metrics, the report noted, the tunnel is about 6.12 times more expensive, meaning it would require six times as much public funding to deliver comparable benefit.
The IST Lab also flagged what it called significant errors in the project’s Detailed Project Report (DPR). It found that the DPR used lower road capacity figures – 3,600 and 2,400 Passenger Car Units per hour (PCU/h) – than what the Indian Highway Capacity Manual would prescribe for the Hebbal flyover’s lanes (4,200 and 2,700 PCU/h), which the study said artificially inflated baseline congestion figures to make the case for the tunnel appear stronger.
It also raised concerns over a sharp 60-metre radius curve near the Esteem Mall exit that would force vehicles to slow from 60 km/h to 40 km/h, potentially reducing capacity and causing queuing; a flood risk given the tunnel’s low-lying entry point near Hebbal Lake, which the DPR allegedly does not adequately address; and unresolved geotechnical concerns about the limited soil support between the lake boundary and existing flyover piers.
The report recommended that authorities prioritise high-capacity public transport solutions such as the metro over standalone road tunnels, citing their superior network-wide congestion relief and stronger benefit-to-cost ratio.
© The Indian Express Pvt Ltd
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