Plans for the Thiruvananthapuram Metro Rail have faced another setback, with uncertainty over national population eligibility norms delaying submission of the revised Detailed Project Report (DPR). Kochi Metro Rail Ltd (KMRL), the implementing agency, said it cannot proceed until there is clarity on the population criteria prescribed under the National Metro Rail Policy, 2017. The Kerala government had earlier approved a 31-km alignment from Pappanamcode to Enchakkal, covering 27 stations. The proposed corridor is designed to link key activity centres, including Technopark, the Medical College, Kazhakkoottam, Akkulam, Thampanoor bus terminal, the railway station, the Secretariat and the international airport. However, the revised DPR being prepared by Delhi Metro Rail Corporation has been put on hold. KMRL managing director Loknath Behera said the DPR cannot be formally submitted without clear guidance on population requirements to ensure compliance with central norms. He noted that adherence to the national policy is essential to avoid the proposal being rejected at a later stage. Under the National Metro Rail Policy, 2017, conventional metro systems are generally intended for cities with an urban population of around 2 million or more. Mr Behera pointed out that an earlier alignment from Neyyattinkara to Attingal met these benchmarks more comfortably than the current proposal. Concerns have intensified following recent Union government decisions. In November 2025, DPRs for the Coimbatore and Madurai Metro projects were returned for failing to meet population and ridership criteria, with the Centre advising consideration of alternative mass transit systems such as BRTS. While Thiruvananthapuram had a population of about 1.68 million as per the 2011 Census and lower estimates for the core urban area, planners argue that the wider metropolitan region is projected to exceed 2.3 million, and excluding this catchment weakens the metro’s case. Despite the uncertainty, the state government remains optimistic, with preparatory infrastructure works already underway along key stretches of the proposed corridor.