BENGALURU: Bangalore Development Authority (BDA) commissioned a study led by an IIT-Bombay professor to assess the traffic effects of its proposed Hebbal short tunnel following widespread criticism of the project.But the August 2026 study, titled ‘Integrated Traffic Microsimulation Study – Bengaluru: Hebbal Flyover & Hebbal Short Tunnel’, prepared by Prof Archak Mittal for Rithwik Projects Private Limited, has now come under scrutiny from IISc and city-based mobility experts, who have flagged gaps in its methodology, data and assessment of traffic benefits.
Data from DPR used
Convener of IISc Sustainable Transportation Lab Prof Ashish Verma, who reviewed the IIT-B study, said the traffic data used in it was sourced from the DPRs provided by the contractor.“The model reports the speed of traffic for 2027 at peak hour in Base Case as 13.74 kmph against 4.29 kmph reported in DPR of the Hebbal Short Tunnel Project,” Verma’s review states, adding that the study did not report queue lengths before and after the interventions, and study methodology was not discussed in detail.Speaking to TOI, Verma also pointed out that there is no ramp at the proposed elevated corridor for vehicles travelling straight towards Windsor Manor.Therefore, only vehicles turning from Mehkri Circle would be able to use the flyover, while a large share of vehicles travelling straight would continue to depend on the existing underpass.He also questioned how the proposed Mehkri Circle elevated corridor would integrate with a larger east-west corridor proposed between Yeshwanthpur and KR Puram.“There was no clarity on how traffic would be handled on existing roads after the proposed projects shift congestion, or how the projects would be integrated,” he said, adding that the environmental impact of such traffic shifts also needed to be assessed.
Old data, outdated conversion factors, no origin-destination survey
Former chief technical adviser to Directorate of Urban Land Transport (DULT), Satyajit Arikutharam, said the IIT-B study was of “extremely poor quality” and had multiple flaws, besides highlighting shortcomings in the original DPRs from which it drew much of its data.He said the study was supposed to examine four scenarios — the base case, each of the two projects separately, and both projects together — but assessed only two: the base case and the combined tunnel-and-elevated-corridor scenario.Arikutharam said the need for the short tunnel cannot be established without fresh survey data, as the traffic data in the DPR predates the opening of an additional ramp at Hebbal flyover in January 2026. “The traffic situation has changed since then,” he said.He also said the DPRs and IIT-B study used 1990-era Passenger Car Unit conversion factors, under which two-wheelers have higher conversion values than those recommended in newer IRC guidelines.This, he said, could inflate the estimated congestion contribution of two-wheelers by around 30%.The IIT-B study itself notes that neither DPR contains an origin-destination study accounting for passengers’ different destinations, he said. Such a study is critical to determine the likely traffic load on one or both projects.Arikutharam also said the study had not considered the impact of a metro line and the proposed long tunnel in its traffic projections.The IIT-B study has also recommended increasing the distance between the elevated corridor and tunnel from 80 metres to 250 metres for more efficient traffic movement. This could require changes to the existing project design, Arikutharam said.
Study commissioned after project faced criticism
A senior BDA official told TOI that the IIT-B study was commissioned after public opposition to the tunnel project. “There was a lot of negative publicity and outcry against the short tunnel road, so we decided to go for another third-party institutional evaluation,” he said.The official said the study found the tunnel and elevated corridor were “very much required” for future traffic and described it as a positive report supporting the project. He said the short tunnel project would be completed by the end of January 2028.
