The real revival of the double decker coaches took place 150 years after the BB&CI's initiative, with the introduction of air-conditioned double decker coaches. A new shell design was developed by the Research Design and Standards Organisation of the Indian Railways, in 2010, which was introduced in commercial service between Howrah and Dhanbad the following year. A new design known as Mark I was developed subsequently, which was introduced in service on the Jaipur-Delhi and Ahmedabad-Mumbai routes. It is interesting to note that the capacity of the new AC Double Decker coach is similar to the four-wheeler ‘Two Storey’ coaches of 1864. The seating and comfort level of modern coaches is, of course, much superior.