The IISc Assessment – Core Findings

Bengaluru Metro Phase‑3: IISc Study Warns Double‑Decker Corridors Could Dampen Ridership

The Indian Institute of Science’s Sustainable Transportation Lab has submitted a technical assessment to the Ministry of Housing and Urban Affairs warning that the proposed double‑decker roadways alongside Bengaluru’s Metro Phase‑3 corridors may cut daily metro ridership and raise emissions. The report projects a fall from 8.09 lakh to 7.98 lakh passengers per day and flags a ₹53 crore surge in project costs, challenging the city’s long‑term mobility goals.

The study juxtaposes a “metro‑only” scenario with a “metro + double‑decker” scenario for the 42 km Phase‑3 stretch. It quantifies the behavioural shift expected by 2041 and translates it into transport‑system metrics.

• ▸Daily metro ridership is projected to drop by 0.11 lakh passengers (≈1.4 %).
• ▸Bus mode share is estimated to fall by 6.4 % while car trips rise by 3.8 %.
• ▸Two‑wheelers and auto‑taxi trips are expected to increase by 1.28 % and 2.8 % respectively.
• ▸The additional road capacity would add ₹53 crore to the overall outlay, mainly for deeper foundations and elevated stations.
• ▸Economic Internal Rate of Return (EIRR) for the double‑decker component falls to 9.07 %, and the overall project EIRR drops to 5.43 %.

These numbers suggest that the extra lanes will not merely accommodate existing traffic but will actively induce private‑vehicle travel, a classic case of induced demand.

Legal and Policy Framework for Urban Transport

India’s transport sector rests on Article 246 of the Constitution, which places roads, railways and related infrastructure under Union jurisdiction. The central government’s National Urban Transport Policy (2019) emphasises modal shift towards mass rapid transit and discourages road‑expansion that fuels private‑vehicle growth. Bengaluru’s own Comprehensive Mobility Plan—approved in 2022—does not list double‑decker corridors among its priority projects.

• ▸Article 246 grants exclusive legislative competence to the Centre for transport matters.
• ▸The National Urban Transport Policy mandates integration of land‑use planning with public‑transit networks.
• ▸The Comprehensive Mobility Plan identifies dedicated bus lanes, non‑motorised transport corridors and metro extensions as core interventions.
• ▸The Ministry of Housing and Urban Affairs (MoHUA) is the nodal agency for approving large‑scale urban infrastructure projects.
• ▸The Bangalore Metro Rail Corporation Limited (BMRCL) operates under the umbrella of the Metro Rail Corporation of India.

Because the double‑decker proposal lies outside the approved mobility blueprint, proceeding without fresh clearances could invite procedural challenges.

Why Double‑Deckers Undermine Public Transit

The engineering premise behind a double‑decked corridor is to segregate fast‑moving traffic from local streets, ostensibly smoothing flow. In practice, however, the added capacity lowers the perceived cost of car travel, prompting commuters to abandon higher‑frequency, lower‑cost metro services. This behavioural shift is amplified in Bengaluru, where the tech‑driven workforce already exhibits a high propensity for private‑vehicle use.

• ▸Induced demand theory predicts that expanding road supply leads to proportional increases in traffic volume.
• ▸Metro ridership elasticity to service quality is high; a perceived decline in convenience (e.g., longer waiting times due to road‑construction disruptions) can trigger mode switching.
• ▸The city’s traffic congestion index has risen by 12 % over the past three years, indicating that existing road capacity is already saturated.
• ▸Air quality monitoring shows a 4 % rise in PM₂.₅ concentrations during peak traffic hours, linked to higher vehicle kilometres travelled.

Thus, the double‑deckers risk creating a feedback loop where reduced public‑transit patronage fuels further road congestion and pollution.

Economic Viability and Environmental Costs

From a fiscal perspective, the project’s EIRR of 5.43 % falls well below the 8–10 % threshold that the Ministry of Finance typically applies to large‑scale urban infrastructure. Moreover, the additional emissions from increased private‑vehicle kilometres conflict with India’s commitment to Sustainable Development Goal 11—making cities inclusive, safe, resilient and sustainable.

• ▸The ₹53 crore cost escalation stems from structural reinforcements required for the double‑decked design.
• ▸Projected fuel consumption rises by an estimated 1.2 % annually, translating into an extra 0.9 million tonnes of CO₂ over the next decade.
• ▸The cost‑benefit ratio, when accounting for environmental externalities, drops to 0.78, indicating a net loss.
• ▸The Ministry’s cost‑effectiveness guidelines recommend a minimum EIRR of 8 % for urban transport projects.
• ▸The study recommends reallocating the additional funds to dedicated bus rapid transit (BRT) lanes, which would improve modal share without inducing private‑vehicle growth.

Implications for Bengaluru’s Mobility Future

If the double‑decker corridors proceed, Bengaluru could see a slower transition to a transit‑oriented city, jeopardising long‑term sustainability targets. Conversely, adhering to the Comprehensive Mobility Plan and prioritising pure metro expansion, BRT corridors, and non‑motorised pathways would align with both constitutional mandates and global sustainability commitments.

• ▸A shift towards private vehicles would increase average commute times by an estimated 7 minutes per trip by 2035.
• ▸The city’s projected population of 12 million by 2035 will place additional pressure on an already strained transport network.
• ▸Aligning with the National Urban Transport Policy could unlock central funding of up to ₹1,200 crore for metro‑centric upgrades.
• ▸Maintaining a high metro ridership is essential for achieving the city’s 2030