Impact of road rationing on modal shift and transport sustainability in Delhi, India

Transport sustainability and its evaluation are important for urban transport planners and policy makers. Some essential methodological frameworks available for evaluating transport sustainability are reviewed in this paper. The work involved measuring modal shift and its effect on transport sustainability by incorporating different indicators and various decision-making techniques during the implementation of an odd–even rationing scheme in Delhi. In this scheme, access to roads is restricted to vehicles based on the last digit of their licence plate (even or odd) on odd or even calendar dates. Eleven sustainability indicators, relevant to transport sustainability and dealing with economic, social and environmental aspects, were considered. Indicators were quantified, normalised and weighted to form sub-indices reflecting social, economic and environmental aspects of sustainability. These three sub-indices were combined to form a single, composite sustainability index (I_cst). Before odd–even rationing, I_cst = 0·841, while the index increased considerably by 6·1% and 5·3% during even and odd days, respectively. The I_cst values showed that the impact of the odd–even rationing scheme was principally an improvement in social aspects, while its impact on environmental aspects was considerably less than expected. The developed I_cst values facilitate scenario comparisons and policy assessment and could be further used by policy makers for future policy implementation and transport sustainability scheme assessments.