Transport Emissions and India’s Diesel Mystery

Comparing Top-Down and Bottom-Up Carbon Estimates

This paper from 2013 Lee Schipper Scholar Sudhir Gota investigates whether the road transport sector in India is showing signs of decoupling of energy consumption with travel demand, or if there are inconsistencies in the official estimates that do not reflect realities on the ground. To determine this, an assessment of top-down (official) estimates based on fuel consumption is contrasted with bottom-up assessment with use of the ASIF framework. It concludes with recommendations on reliability of top-down and bottom-up estimates in India.


Key Findings

Executive Summary

In India, official statistics on fuel consumption in the road transport sector indicate a possible decoupling of road transport energy consumption and transport demand from 1995 to 2005. In that period, transport sector fuel consumption does not show any increase, while over the same period the number of registered vehicles increased threefold, freight activity (ton-km) increased by more than two times, while gross domestic product (GDP) per capita increased by more than 5% annually.

But is this really good news?

The main objective of this research is to reconcile official fuel consumption data (i.e. top-down) with bottom-up quantifications and identify potential discrepancies. Using bottom-up studies conducted by different researchers and by developing a baseline with different scenarios, various issues are identified for improvement.

It was found that official statistics on road transport fuel consumption do not provide enough explanation for and insights on the growing travel demand. The main issue with the top-down data was the allocation of diesel into different sectors, and this was the main source of variation between top-down and bottom-up estimates. Bottom-up scenarios developed in this analysis suggest that official fuel consumption data seems to overestimate diesel consumption before 1995 and under-estimate fuel consumption after 1995, and both these variations are very high in magnitude.

The trends and scenarios in this research explain and establish the need to use bottom-up modelling for policy making and to prioritize diesel vehicle data collection to improve bottom-up transport modelling in India. 

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