Bengaluru Hebbal Tunnel Study Faces Traffic Data Questions
Bengaluru’s proposed Hebbal short tunnel has entered a fresh technical debate after experts questioned the data and methodology behind a traffic study commissioned to assess the project. The study, led by an IIT Bombay professor, supports combining the tunnel with an elevated corridor, while researchers from the Indian Institute of Science have raised concerns over outdated traffic inputs, missing scenarios and gaps in the modelling.
The Bengaluru Hebbal Tunnel study was commissioned by the Bangalore Development Authority after sustained criticism of the proposed infrastructure. Prepared in August 2026 for the project contractor, the report examined traffic around Hebbal Junction, Mekhri Circle, Ballari Road, the Veterinary College area and the surrounding road network. Its central recommendation was that the tunnel and elevated corridor should operate as complementary routes rather than being assessed as competing projects. The review by IISc researchers has questioned whether the study provides enough evidence for that conclusion. One concern is that much of the traffic data was drawn from existing Detailed Project Reports rather than fresh independent surveys. The review also pointed to a large difference between projected 2027 peak-hour speeds in the new model and figures contained in the original tunnel DPR, raising questions about how the assumptions were reconciled. Mobility experts have also highlighted the absence of an origin-destination survey. Such data is important for understanding where vehicles are travelling from and to, rather than simply measuring traffic volumes at individual points. Without it, predicting how motorists would distribute themselves between existing roads, a tunnel and an elevated corridor becomes more uncertain. Another issue concerns the scenarios tested. The study was expected to consider the existing network, the tunnel separately, the elevated corridor separately and the two projects together. Critics say the analysis effectively concentrated on the base case and the combined intervention, limiting the ability to compare the individual contribution of each project.
The experts have also questioned the use of older Passenger Car Unit conversion factors and the failure to incorporate changes to the road network since the original DPRs were prepared. The opening of an additional Hebbal flyover ramp in January 2026 is one such change that could alter current traffic patterns. The review also raises questions about how future Metro expansion and the proposed long tunnel could affect demand.The project’s traffic case is especially important because the Bengaluru Hebbal Tunnel carries a substantial environmental cost. More than 1,100 trees have been identified for removal along the proposed corridor, while the alignment is close to Hebbal Lake. Earlier IISc analysis had warned that congestion could be shifted towards tunnel entry and exit points and had also raised concerns around flooding.The debate therefore extends beyond a disagreement between academic institutions. Before major urban infrastructure locks in long-term costs, traffic models need current data, transparent assumptions and comparable alternatives.Publishing the underlying traffic counts, modelling methodology and scenario results would allow independent experts and citizens to assess the project’s expected benefits.
For Bengaluru, the immediate planning priority is to establish whether the proposed interventions will genuinely improve network-wide mobility or redistribute congestion elsewhere. That evidence is particularly important when the project also carries significant ecological and financial implications.
