(1) Use of efficient engines to reduce the amount unburnt hydrocarbons emission .

(2) Use of catalytic converter filter in the vehicle that reduce the amount of toxic gases.

(3) Use of good quality of fuel.

(4) Use of unleaded petrol to reduce the load of lead in the exhaust.

(5) Use of CNG (compressed natural gas) to  lower the toxic contaminants in the exhaust.