You get a confirmed reservation on one of the lower berths. Then a senior citizen comes and requests you to exchange your seat with a middle / upper berth seat. It’s not uncommon to see young people exchanging their seats with pregnant women, old ladies, and senior citizens for their convenience. To address this issue, Indian Railways has devised SS quota or commonly known as a lower berth quota in trains. Since elder people face difficulty while climbing onto middle or upper berths, Indian Railways has provided them with the facility to book tickets for lower berths in a train.