It is very obvious that number of motor cycles, cars, autos, and buses are increased in the cities due to the increase in the comfort level of people and their demands. Every vehicle produces harmful carbon monoxide, which is indeed a deadly harmful chemical. Especially, during traffic signals, vehicles are not switched off and produce heavy quantity of poisonous smoke which is of no use, even extra fuel is wasted. It happens a lot in metro cities including a place like Hyderabad. I think people should put their keys off during traffic signals or during traffic jams.