The authority would now have to spend additional money to purchase these train sets after an obstacle was found in Chennai Metro Rail Limited's proposal to lease up to 42 driverless trains. The initial strategy indicated a way to lower the project's cost from Rs 890 billion to Rs 618.43 billion by leasing the 42 metro trains rather than buying them. After the CMRL discovered that businesses do not lease metro trains because they cannot be used elsewhere after the lease period has ended, the plan has now been abandoned.

The CMRL plan requires 138 three-car trains to run on Chennai's 118.9-kilometer Phase-2 metro network. This phase is expected to be public in 2026. According to a CMRL official, after meeting with train manufacturers from around the world to learn why subway trains are not leased, They found that because subways are made specifically for a city or a subway line, companies that lease them can't roll them back and use them elsewhere in the event of a problem. After finishing the tender seeking expressions of interest in December 2021 because only one company responded and submitted an application, CMRL started discussions with train manufacturers.

However, as long as the signalling software remains the same, long-distance and suburban trains run can be rented by the railways and used elsewhere. "We may need nearly $1 billion to Buy these trains. We've talked about it with the state government, and they might be able to cover the costs. Now all you have to do is issue tenders, an official reportedly told the Times of India."

Phase 2 of the Chennai Metro will require 414 carriages or 138 three-car trains when operations begin in 2025, according to the detailed project report (DPR). 762 carriages (254 three-car or 127 six-car trains) will be needed in three decades. The insider added that the subways initially three carriages and that the goal is to have trains with low capacity but with high frequency.