Optimizing assembly line productivity in passenger car manufacturing: a comprehensive review with evidence from the Pune automotive region

Passenger car manufacturing in India is undergoing a rapid transformation driven by growing demand for high productivity, sustainability, and more flexible assembly systems. Even though significant progress has been made, existing studies mostly focus on individual techniques such as Lean, automation, or digitalization and rarely provide a unified framework for productivity improvement. This review tries to fill that research gap by analyzing productivity drivers across multiple dimensions, including technical, ergonomic, digital, policy, and regional aspects, with a focus on Pune’s automotive cluster. The objective is to synthesize evidence-based strategies to optimize assembly line performance. A mixed-method approach was used, consisting of a literature review covering 2010 to 2025, along with a regional benchmarking meta-analysis on industrial case data. Metrics such as overall equipment effectiveness, process cycle efficiency, and takt time are used as core indicators in the study. Key findings indicate that Lean Six Sigma implementation improved process cycle efficiency (PCE) from 19.9% to 66.7%, cobot integration increased overall equipment effectiveness (OEE) from 80% to 87.74%, while scrap generation reduced from 0.06% to only 0.02%. Ergonomic redesigns of workstations led to a 9.7% gain in productivity. Digital twin simulations have shown that throughput increases up to 20%, and IRPA adoption resulted in a simulated workforce reduction of 45.69%. Policies such as Make in India PLI hold promise, yet challenges remain in terms of EV infrastructure localization. An integrated Lean–AI–digital model, when supported with ergonomic design and policy alignment, can possibly deliver 25%–40% improvement in productivity, especially in manufacturing hubs like Pune.