How could use of ICTs make transport systems in large cities sustainable? To what degree would then everyday patterns of action, in which use of ICT is becoming increasingly integrated, be an effective force in such sustainable development? In this paper we use own and other ethnographic studies of how people travel and plan their travel in large Nordic cities and explore a couple of scientific articles built around scenarios of sustainable development of ICT-supported transport in large cities. In the scenarios the role of ICT was most prominently for travel planning, collective ownership and/or access to vehicles, payment systems and traffic management for environmental purposes. Two of the scenario articles were selected for a closer analysis. In the ethnographic material sub-practices, critical for transport in everyday life, were identified. The aim was to show if and how proposed solutions in the sustainability scenarios are possible and meaningful for urban dwellers to integrate into their everyday travel practice. We found that scenarios of this kind might benefit from being supplemented with certain components. We discuss how actors that currently develop traffic management, mobility and travel planning services are somewhat blind to some significant parts of the whole spectrum of relevant social practices. We also discuss how this could provide conditions for actors and stakeholders to highlight and facilitate sub-practices with ICT use and in line with sustainable development. We tentatively discuss and propose that authorities responsible for urban transport set goals for maintaining and spreading certain practices, related to sustainability impacts. In this way the development of everyday social practice among city residents could be supported as an effective force in the development of the city's transport system, specifically including the development of ICT in relation to transportation.