An energy efficient mass transportation model for Gauteng

Abstract

Public transportation in South Africa is characterized by little or no consideration for energy efficiency and use of cleaner fuels. In the case of transport planning in South African cities, no assessment of the economic or environment impact of limited or highly priced electricity or conventional liquid fuels has been included in the decision-making process. Recent examples of the Gautrain and the Bus Rapid Transit programmes (both in Gauteng) reinforce this weakness in current planning methodologies. This study has focused on the need to introduce energy efficiency and greenhouse gas consideration in mass transport decision-making in Gauteng. The intention of the study was to produce a strategic modelling tool that would be a high-level product for politicians to use. At the same time, the tool should feature more advanced capabilities such as optimisation algorithms to satisfy specific objective functions, such as time, cost, energy or global warming potential. In this way, sensitivity studies based on different orderings of these objective functions could be undertaken using this model. The model's performance was tested using two different scenarios. In the least time scenario, which is practically the base case, the order of optimisation was time first, then cost, then energy and then global warming. The constraint on objective functions was relaxed by 10% after each optimization to get to the final result, which is then understood to be the least global warming impact for a particular plan that was initially optimized for time. In the least global warming scenario, the order of optimisation was changed, with first global warming, then energy, then time and then cost optimised. The resultant plan is the lowest cost plan that could be developed if global warming was the most important consideration. The results obtained for both scenarios are discussed and compared to each other where practical. Where possible model verification and validation have been undertaken and where it has not been possible, the approach to be taken in a follow up study will serve to provide such validation. The model has been shown to be an effective high-level strategic decision-making tool. It is a tool that should be used by politicians and transport planners alike to ensure energy efficiency and greenhouse gas reduction are factored into future transport options considered.