The affordability of our transport systems determines not just how we travel but also how far, when and, most importantly, if we travel at all. While physical
access is key in planning for transport systems and solutions across the world, affordability has been explored largely in academic circles, and is mostly related to the topics of social inclusion and travel poverty.
Previous studies in the UK show that the availability of transport, whether private or public, is not always a factor in social exclusion, and that it is only where the price of transport exceeds affordability that social exclusion occurs. A study in Bogotá revealed that, in poor areas, reducing fares is cheaper and more effective than increasing speeds. Another paper looking at the expansion of the London bicycle sharing scheme in poorer areas of the city concluded that when fares increased the benefit of the expansion was partially offset.
In balancing physical access and affordability, transport systems are designed to make use of the sharing model which manifests itself either in the relatively rigid form of public transport or the more flexible form as 2+ car sharing, bike-sharing and car clubs. A recent study in the US, ‘Shared Mobility and the Transformation of Public Transit’, concluded that shared-use modes expand options for lower income households and that 6% of the lowest-income group would not even undertake a trip if their shared option was not available. 
Similarly Liftshare found that, in the Yorkshire and Humber region in the UK, 10% of informal car sharers and 18% of formal use it because of lack of alternatives or access to public transport. In addition, research undertaken by Steer for car club operator Co-wheels in the UK shows that their second largest user group is represented by ‘urban squeeze users’, characterised by living in urban areas, and having low car ownership, being less wealthy than the UK average, with many finding it difficult to cope on their income. For this group, having access to the car clubs alleviated travel poverty by enabling users to access a car or to make trips that previously they would not have been able to undertake.
At the global scale, evidence  is emerging regarding the potential of shared transport and technologies such as connected and autonomous vehicles (CAVs) to change the mobility paradigm and car ownership models in the decades to come, to make cities more liveable and accessible.
Despite this, managing the balance between increasing accessibility and maintaining affordability for a greater proportion of the population, without generating or increasing inequality and social exclusion, remains the biggest challenge going forward, both for the more traditional modes of transport and for shared solutions and on-demand services. 
One of the main reasons for this is the reliance on information collected from people who currently travel to optimise existing systems or create new services. This creates an involuntary blind spot on the travel needs of everyone else who does not travel. That is why cab aggregators have started partnering with retailers and companies with data aggregating capabilities to anticipate the next travel needs of customers, based not solely on their past travel patterns but also on other things such as shopping preferences.
To open up a more informed discussion about affordability and travel opportunities, we need to expand the sources of information used to analyse travel needs and specifically to start asking questions about the trips that do not happen as much as about the trips that do.
A key element of this discussion will remain whether cities have the resources to form meaningful partnerships and to harness the intelligence provided by such data to shape transport system that are both accessible and affordable. Opening up the travel market to the entire population of a city can be the new disruptive achievement of intelligent mobility.
Preston, J and Raje, F (2007), Accessibility, mobility and transport-related social exclusion. Journal of Transport Geography, 15, (3), 151-160
Bocarejo, J.P.S., & Oviedo, D.R.H. (2012), Transport accessibility and social inequities: a tool for identification of mobility needs and evaluation of transport investments. Journal of Transport Geography, Article in Press.
Goodman, A; Cheshire, J (2014) Inequalities in the London bicycle sharing system revisited: impacts of extending the scheme to poorer areas but then doubling prices. Journal of Transport Geography, 41. pp. 272-279.