Potential for mitigating greenhouse gases through expanding public transport services: A case study for Gauteng Province, South Africa

South Africa's Province of Gauteng is a fast growing megacity region including the cities of Johannesburg and Tshwane. Increasing population and prosperity lead to a steadily growing energy demand and thereby increasing greenhouse gas (GHG) emissions. One third of the province's final energy consumption comes from the transport sector, dominated by motorized individual transport. Due to the limited financial resources to fund public transport initiatives, the most cost-effective means to reach the GHG mitigation targets are intended, without jeopardizing the economic growth. Recently, a bus rapid transit (BRT) system (Rea Vaya) and a rapid rail link (Gautrain) have been introduced to enforce the public transport system. In this paper, we investigate planned and possible future network expansions of the BRT and the Gautrain in terms of transport performance, costs of network expansions and GHG mitigation potential. Based on a trip rate model, we show that extensions of the current network can increase passenger numbers significantly (between 320% and 660% between 2013 and 2040 depending on the framework conditions). However, despite these expansions, the modal share of the BRT and the Gautrain in total passenger-kilometres travelled remains below 4% until 2040. This results in a decrease of cumulated GHG emissions of less than 1% until 2040 and relatively high GHG mitigation costs (4948-30045 ZAR2013/t CO2e). Nevertheless, a better integration of all public transport systems can increase the attractiveness of the services, which can result in a higher modal shift from private cars and thereby higher GHG emissions reductions at lower costs.