When Delhi Metro Rail Corporation managing director Mangu Singh was growing up in Najibabad, Uttar Pradesh, he walked ten kilometres to school and back daily. Now, he runs a high-tech mass-transit system in Delhi which every city wants and some, like Kochi, Agra and Jaipur, are getting or already have. In an interview with Pragya Singh, he talks about self-appraisal and the nitty-gritty of managing an engineering-led enterprise. Excerpts: