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 calls for 138 three-car trains to operate on Chennai's 118.9 kilometre phase-2 metro network. In 2026, this phase is anticipated to be public. According to a CMRL official, after meeting with train manufacturers from around the world to learn why metro trains are not leased, they discovered that because metro trains are made specifically for a city or a metro line, businesses that lease them cannot roll them back and use them elsewhere in the event of a problem. After terminating the tender seeking expressions of interest in December 2021 because only one business answered and applied for it, CMRL initiated discussions with train manufacturers.

However, as long as the signalling software remains the same, long distance and suburban trains run by the railways can be leased and utilised elsewhere. "We may require close to $1 billion to purchase these trains. We've talked about it with the state government, and they might be able to cover the expense. Now, all that is left to do is issue tenders, an official reportedly told the Times of India.”

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