Sir — It is a common saying that big cities have bigger problems. This holds true for Delhi too. Although the city has to deal with numerous challenges, tackling air pollution is the one which needs immediate attention. An aerial view of the city will show hundreds of vehicles lined up at a signal. Higher authorities have to come up with a plan to deal with it. There is sufficient evidence available to support the fact that the use of public transport reduces air pollution. This is because public transport replaces many emissions-producing private vehicles with few transit vehicles. The relevant department must take steps to improve transportation system to make the environment cleaner