Is rail cleaner and greener than bus? Corinne Mulley a , David A. Hensher a,⇑ , David Cosgrove b a Institute of Transport and Logistics Studies, The University of Sydney Business School, The University of Sydney, NSW, Australia b Bureau of Infrastructure, Transport and Regional Economics, Canberra, ACT, Australia article info Article history: Keywords: Bus and rail emissions Greenhouse gases Comparative assessment Environmental impact Fuel cycle Vehicle life cycle Australia abstract The popular consensus is that urban passenger rail is more environmentally friendly than urban passenger bus. This position is largely associated with the key energy source for each mode, respectively electricity and diesel, where electric vehicle use will typically result in local air quality improvements away from the electricity generation source. Surveys of community perceptions reflect this sentiment; however the relationship between the source of energy and its resultant emissions is not something that citizens fully under- stand. There is a general lack of awareness of the resource base of much of electricity gen- eration in some countries. Where generation sources are suitably renewable or low-carbon, electricity use will offer greenhouse gas abatement potential. However, in countries which still rely heavily on coal-fired power stations, such as Australia, abatement is not as assured and estimating emission outcomes can require careful assessment. Supporters of alterna- tives to diesel use can focus on the future supply of fossil-fuels, an argument which has merit; however such arguments are often confounded with environmental qualities related to local air pollution and enhanced greenhouse gas emissions. This paper takes a close look at the greenhouse emissions that are associated with urban rail and bus in Australia. Estimated intensities, when presented in the context of effective service delivery (primarily in terms of emissions per passenger kilometre), raise questions about the distortions that are present in the widespread promotion in Australia (at least) of rail as a more environ- mentally friendly and hence a sustainable mode of urban passenger transport than bus. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction: The policy setting The case for investment in urban public transport is indisputable – to not only offer a real alternative to the car, but to support the broader objectives of integrated transport and land use planning that can deliver efficient and effective acces- sibility that also aligns with notions of wellbeing, social inclusion and environmental sustainability (see Stopher and Stanley, 2014). Within the set of public transport options, governments have in the main focussed on supporting a mix of road and rail-based modes; and depending on the historical evolution of a specific urban area, the extent to which one mode has dom- inated the other is clearly visible. In Australia, for example, the capital cities are typically dominated by radial heavy rail which is a reflection of their historical developments. It is generally understood that cities which evolved in the automobile era are very much the product of roads that service urban sprawl, where bus services have been the offered public mode because of the availability of roads. Nineteenth and http://dx.doi.org/10.1016/j.trd.2016.12.004 1361-9209/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail addresses: Corinne.Mulley@sydney.edu.au (C. Mulley), David.Hensher@sydney.edu.au (D.A. Hensher), David.Cosgrove@infrastructure.gov.au (D. Cosgrove). Transportation Research Part D 51 (2017) 14–28 Contents lists available at ScienceDirect Transportation Research Part D journal homepage: www.elsevier.com/locate/trd