Environmental issues in Iran include, especially in urban areas, vehicle emissions, refinery operations, and industrial effluents which contribute to poor air quality. Most cars use leaded gas and lack emissions control equipment. Tehran is rated as one of the world’s most polluted cities. However, buses and cars running on natural gas are planned to replace the existing public transportation fleet in the future. Also, energy prices are kept artificially low in Iran through heavy state subsidies, resulting in highly inefficient and polluting consumption patterns. Traffic management, vehicle inspection, general use of electric bicycles and electronic government are also part of the solution.