citizens over the years not particularly known for their love for discipline delhiites started displaying their best behaviour once inside the sanitised environs of metro stations and trains barring a few exceptions in the rather long time of 15 years delhi metro has also been able to keep its stations largely clean of the ubiquitous paan stains and carelessly thrown litter this has been made possible by not only roundtheclock cleaning but also delhiites keeping their primal instincts in check while on the metro premisesduring the initial years of expansion of delhi metro there were many engineering challenges it had to overcome be it crossing river yamuna tunnelling through rocky terrain and under buildings that were hundreds of years old or crossing wide railway lines and roads where pillars couldnt be constructed apart from a few tragic accidents such as the ones at laxmi nagar and zamrudpur where fatalities resulted delhi metros track record has largely been unblemished the challenge of building the urban train network has now been largely replaced by the daunting task of ensuring smooth operations across its vast network across delhincras delhi metro completes 15 years the city looks forward to the start of phase iv which would see the network reaching the fringes of the capital in the next five years delhi metros network would be equal to the largest metro networks in the world and the challenge for dmrc would be to maintain its mostly impeccable record as delhis most reliable and comfortable mode of public transportwatch watch some amazing features of delhi metros magenta line that you must know