Sailors who died of scurvy, a disease caused by the deficiency of vitamin C, between the years 1500 and 1800

Metro trains carried 5,400cr people in 2017; number set to multiply in next 5 years

Across the world, 30 new metro systems started during 2000-09. Another 45 will be completed by 2019, and more than 200 are expected to open in the next five years. Most of these are being built in Asian cities, and quite a few are in India. Cities are investing heavily in metro systems because of the increasing pressure of population. As large numbers of people in developing countries move to cities in search of work, the existing transport infrastructure based on private vehicles and buses is tottering. Pollution levels have also risen sharply. Metro systems promise a clean, efficient and fast alternative to the mess on city roads.