CNG and diesel urban buses in India: A life-cycle cost comparison

Delhi’s bus fleet is powered by compressed natural gas (CNG) to address poor air quality. CNG has also been implemented in buses in other Indian cities. We evaluate the life-cycle costs (LCCs) of the Standard (high-floor), low-floor, and low-floor air-conditioned CNG buses and their diesel counterparts in India. Given the importance of fuel economy and fuel price for fuel costs, we analyze the sensitivity of the LCCs to these factors. Also, to assess the effect of fuel prices if they were market driven, we evaluate the LCCs of low-floor air-conditioned CNG and diesel buses in India, but with US fuel prices. Our study aims to inform decision-making regarding the implementation of CNG buses, in concert with an assessment of their environmental and health benefits.The LCCs for CNG are higher than for diesel, but CNG negatively affects the LCC of Standard buses proportionately more than for the low-floor buses. The LCC is significantly higher for the low-floor air-conditioned, relative to that of the low-floor, and in particular the Standard, CNG buses. The significantly higher LCCs for the low-floor and low-floor air-conditioned buses, even for diesel, raises the questions of whether these buses are justified by increased patronage, and how they affect transit supply and affordability.The fuel price and fuel economy of CNG are critical for the competitiveness of CNG relative to diesel buses. This, along with the wide variation in CNG and diesel prices, demonstrates the need for careful fuel pricing policies when CNG is implemented in bus transit.