21 April 2026

A conference paper submitted by the ACUMEN partners to hEART 2025 takes a fresh look at what seamless mobility actually means 

Getting from A to B without a hitch sounds simple enough. But anyone who has missed a connecting bus, fumbled with three different ticketing apps or stood confused at a poorly signed interchange knows that seamless travel is easier said than delivered. A recent study from researchers at Aalto University, Université Gustave Eiffel and the Technical University of Delft set out to ask a deceptively simple question: what does seamless mobility actually mean, and what do we know about how to achieve it? 

The answer, it turns out, is more complicated than the word suggests. 

The term “seamless mobility” has been used widely in transport research and policy for years, but rarely with much precision. Different studies use it to mean different things, from smooth transfers between buses and trains, to integrated ticketing, to the broader idea of a transport system that simply works well for its users. This ambiguity, the authors argue, is a problem. Without a clear and shared definition, it becomes harder to measure progress, compare findings or design interventions that actually improve things. 

To address this, the research team conducted a systematic review of 2,205 studies published between 2008 and 2024, ultimately distilling these down to 91 that directly addressed seamless mobility in a meaningful way. The review was structured around a four-layer framework, covering infrastructure, transport modes, system management and the user interface, which together are intended to capture the full range of factors that shape whether a journey feels seamless or not. 

The infrastructure layer covers the physical foundations of any transport system: roads, rail lines, interchange hubs and the network connections between them. Research in this area tends to focus on how to make better use of existing infrastructure rather than simply building more, given the constraints of dense urban environments. Minimising transfer distances at interchange hubs, improving road design and using connected sensors to monitor and manage traffic flows all represent infrastructure improvements that could unlock seamless mobility. 

The transport modes layer looks at the vehicles and services that run on that infrastructure, from buses and trains to shared bikes, ride-hailing services and autonomous shuttles. Shared mobility in particular has attracted growing research attention, with studies showing that ride-hailing and bike-sharing can improve first and last-mile connections and reduce the gaps between existing public transport services when used as a feeder. Automated vehicles also feature here, though the review found only two studies that directly linked autonomous vehicle technology to seamless mobility, suggesting this remains an underexplored area with benefits for Public Transport remaining to be proven. 

System management covers the data, analytics and coordination tools that keep transport networks running efficiently. This is the largest category in the review, accounting for 26 of the 91 studies. Much of the work here focuses on multimodal travel reliability, including how systems like Mobility as a Service can integrate public transport, bike-sharing and carpooling into a more coherent offer, and how traffic management strategies can be applied across modes to reduce delays and improve connections. 

The user interface layer, which includes mobile applications and integrated ticketing systems, looks at how passengers actually access and navigate the transport system. Despite being the layer most immediately visible to users, it received comparatively little research attention, with only 11 studies in this category. The authors note that while technology has made user interfaces considerably more sophisticated in recent years, this area remains underrepresented in academic literature relative to infrastructure and system management. 

Across all four layers, a consistent set of criteria emerges for what seamlessness actually means in practice: reduced transfer distances, shorter travel times, improved reliability, better accessibility and more convenient payment and route-finding tools. These criteria provide a useful reference point for assessing whether transport systems are genuinely moving in the right direction. 

The review also highlights where research attention is concentrated and where gaps remain. Infrastructure and system management dominate the literature, while transport modes and user interfaces receive less attention. Reliability across multimodal journeys is the single most studied aspect of seamlessness, which the authors describe as an unsurprising finding given how central reliability is to any transport system’s performance. More unexpected is the relative neglect of user interface research, given how much the digital layer of transport has changed in recent years and how directly it shapes passengers’ experience. 

Emerging technologies, particularly the Internet of Things and automation, are beginning to reshape all four layers. IoT applications have already enabled new forms of shared mobility and made existing infrastructure more efficient. Automated vehicles, while still limited in deployment, are being tested in specific contexts such as autonomous shuttles in city centres where conventional transport struggles to operate. 

The study does not claim to have solved the definition problem once and for all. It presents itself as an initial step in a broader systematic review, and the authors are candid about the work still to be done. But by mapping the existing literature onto a coherent framework and identifying where research is concentrated and where it is thin, the paper provides a useful foundation for both researchers and practitioners. 

For cities and transport authorities working to improve the passenger experience, the four-layer framework offers a practical checklist of sorts. A genuinely seamless journey requires not just good infrastructure or well-run services in isolation, but coordination across all four layers simultaneously. A well-designed app is little use if the interchange it directs you to is poorly laid out. Integrated ticketing means little if the services it connects are unreliable. Seamlessness, in short, is a system property, not a feature of any single component.