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The Impact of Delhi's CNG Program on Air Quality


  • Narain, Urvashi

    () (Resources for the Future)

  • Krupnick, Alan J.

    () (Resources for the Future)


This paper estimates the impact on Delhi’s air quality of a number of policy measures recently implemented in the city to curb air pollution using monthly time-series data from 1990 to 2005. The best known of these measures is the court-mandated conversion of all commercial passenger vehicles—buses, three-wheelers, and taxis—to compressed natural gas (CNG). Broadly, the results point to the success of a number of policies implemented in Delhi but also to a number of areas of growing concern. For example, the results suggest that the conversion of buses from diesel to CNG has helped to reduce PM10, CO, and SO2 concentrations in the city and has not, contrary to conventional wisdom, led to the recent increase in NO2. At the same time, however, the conversion of three-wheelers from petrol to CNG has not had the same benefit, possibly because of poor technology. Another policy measure that appears to have had a positive impact on air quality is the reduction in the sulfur content of diesel and petrol. This has led to a decrease in SO2 levels and, because of conversion of SO2 to sulfates (a fine particle), a decrease in PM10 concentrations. Some of these gains from fuel switching and fuel-quality improvements are, however, being negated by the increase in the proportion of diesel-fueled cars, which is leading to an increase in PM10 and NO2 levels, and by the sheer increase in the number of vehicles.

Suggested Citation

  • Narain, Urvashi & Krupnick, Alan J., 2007. "The Impact of Delhi's CNG Program on Air Quality," Discussion Papers dp-07-06, Resources For the Future.
  • Handle: RePEc:rff:dpaper:dp-07-06

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    References listed on IDEAS

    1. Lucas W. Davis, 2008. "The Effect of Driving Restrictions on Air Quality in Mexico City," Journal of Political Economy, University of Chicago Press, vol. 116(1), pages 38-81, February.
    2. Akie Takeuchi & Maureen Cropper & Antonio Bento, 2007. "The Impact Of Policies To Control Motor Vehicle Emissions In Mumbai, India," Journal of Regional Science, Wiley Blackwell, vol. 47(1), pages 27-46.
    3. Henderson, J Vernon, 1996. "Effects of Air Quality Regulation," American Economic Review, American Economic Association, vol. 86(4), pages 789-813, September.
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    More about this item


    air pollution; compressed natural gas; low-sulfur diesel; diesel-fueled cars; Delhi;

    JEL classification:

    • Q53 - Agricultural and Natural Resource Economics; Environmental and Ecological Economics - - Environmental Economics - - - Air Pollution; Water Pollution; Noise; Hazardous Waste; Solid Waste; Recycling
    • R41 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - Transportation Economics - - - Transportation: Demand, Supply, and Congestion; Travel Time; Safety and Accidents; Transportation Noise
    • R48 - Urban, Rural, Regional, Real Estate, and Transportation Economics - - Transportation Economics - - - Government Pricing and Policy

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