Even though they have been around for some 50 years, bike sharing schemes (BSSs) have in recent years witnessed a dramatic growth in cities in the UK, elsewhere in Europe, North America, East Asia and to some extent Latin America and Australia (for overview of the current spatial distribution, see  http://bikes.oobrien.com/global.php and  http://bike-sharing.blogspot.co.uk). Recent schemes differ enormously in terms of size, governance and business models. Compare, for instance, Hangzhou‘s mammoth scheme which is initiated, provided and run by the local state with Oxford‘s recent BSS experiment with 30 bikes and 6 docking stations that has been initiated by the county council but provided and run by a private company.

Intuition would suggest that BSS help to reduce energy consumption in urban transport, but I don’t think we really know much about their energy implications, for various reasons. First, on top of the existing diversity in schemes, the growth in both the number of schemes and size of individual schemes means that the social practices in which shared bikes are enrolled and hence the energy implications are diversifying rapidly. This increases uncertainty about energy implications. Second, there is a lack of appropriate data. This claim may appear counterintuitive given that most 3G and 4G schemes are hailed for the unique data they generate. But these data suffer from similar limitations as many other ‘big data’ on transport in being extensive but also thin on actual content. They either show which bikes are docked at (many) specific moments at particular stations, or where in physical space a given bike is at particular times. At best, we can reconstruct high-resolution space-time trajectories of individual bikes, but learn little about how bikes become coupled to and enrolled in the space-time paths (time-geography) and activity/travel patterns (activity-based travel behaviour analysis) of individuals, or in social practices (practice theory). Neither do we currently know much about how the space-time trajectories of shared bikes are related to those of other, motorised modes of transport. Consequently, as far as I am aware, there is little or no robust evidence that BSS usage actually substitutes for more energy-intensive ways of moving around the city, or about the extent to which schemes generate new demand for mobility. The nascent, and often rather celebratory, academic literature on BSS usage tends to examine trip patterns in isolation from wider urban transport systems. What is known on substitution comes either from modelling studies, in which all kinds of often strong assumptions about modal choice and substitution are made, or from studies using questionnaires with general questions about mode use that often lack the required precision, validity and reliability.

That said, there are good reasons why BSSs might help reduce energy consumption. Not only are the embedded energy and greenhouse gas emissions likely to be much lower for a BSS than for a bus, light rail or car system of the same spatial extension (a life cycle analysis examining this conjecture would be useful!);  by reducing the ‘last mile’ problem of ‘egress’ transport from a public transport stop to one’s final destination, a BSS can – if integrated adequately into a multimodal transport system – increase the attractiveness of public transport for people who might otherwise be using a private vehicle. BSS usage in a city context also generates all kinds of indirect effects, which might even exceed direct modal substitution effects. Use of shared bikes for utilitarian trips, for instance by people commuting into London by train seeking to reach their final destination, may increase those people’s inclination to cycle in other situations, for instance around the home for non-work trips. Widespread use of shared bikes in cities may also increase skills and competency among a range of road users: cyclists may begin to feel more confident in using bikes in other contexts, including those where conditions (infrastructure, actions of other road users) are less conducive to cycling, and drivers of cars and goods vehicles become more attuned to sharing the road with cyclists, possibly to the extent that subconsciously reckoning with cycling at left turns and other risk traffic situations becomes second nature. This reasoning obviously is a variant of the more widely known ‘safety in numbers‘ argument.

The question of energy consumption should not only be looked at through a lens of instrumental rationality and effectiveness; issues of social justice should be considered as well. Few studies have so far examined the social distribution of benefits, but the limited work that is available suggests that white, middle-class men are most likely to regularly use a BSS (e.g. Goodman and Cheshire 2014). It would appear that BSSs do little to address inequalities in access to transport that exist in most cities. Perhaps this is not surprising if the proactive approach of many local governments regarding BSS is placed in a wider context of urban entrepreneurialism and government-led, pro-growth oriented gentrification and regeneration. Having a BSS in a city is then not merely about environmental or social sustainability (air quality, GHG emissions, redistribution) but – and perhaps primarily – about creating an environment capable of attracting the mobile capital of firms, tourists and prospective residents by offering a transport scheme that is both fast and congestion-free, and fashionable and fun. There are also opportunity costs: pouring public money into a BSS probably means that less funds are available for more socio-spatially inclusive initiatives that can promote cycling as an energy-efficient means of urban mobility, such as bike co-ops, maintenance workshops or cycling competency training. Community-led, grassroots initiatives should not be romanticised and many in UK cities are to some extent supported by councils, but it would appear that these activities have greater potential than BSSs to reach migrant communities, the elderly and the urban poor and thus to link energy efficiency aims with progressive public health and social agendas.

BSSs have potential to reduce energy consumption in urban transport, if adequately integrated in a wider multi-modal transport system and as long as they do not constitute the mainstay of cycling policy and local governments’ financial support for cycling. It is a cliché to say that more research is needed, but we really need to know much more about how BSS usage is shaping and shaped by social practices in the city, what its energy implications are, and how BSSs link in with pro-growth agendas that do little to redress the soaring inequalities in mobility, life chances and health in contemporary British cities.