What happens in between walking and intermodality

Every journey we take is more than just the vehicle we ride in; it is a sequence of small movements that stitch together our daily lives. Before we can board a train, we must walk to the station. After we step off a bus, we must walk to our office or home. In between two different modes of transport, we often walk again to bridge the gap. These walking segments are the invisible glue of modern travel, yet they are frequently overlooked in how we plan cities and design transport systems. When people combine a car, a bus, and a train in a single trip, this is called intermodality. It is a strategy increasingly seen as essential for reducing pollution and congestion, as it offers a flexible alternative to driving alone. However, while city planners know that people walk to catch their ride, they often treat these walking parts as simple, uniform steps. They assume that the distance a person walks to get on a bus is the same as the distance they walk to get off, or that the effort required to switch from a train to a tram is predictable and fixed. This study asks a deeper question: does the context of the trip change how people walk? Does the reason for the trip, the type of vehicle used, or the position of the walk within the journey change the distance covered or the time spent on foot?

To answer this, researchers in Geneva, Switzerland, turned to the real-world movements of 723 volunteers. Over a period of two weeks in late 2024, these participants carried GPS trackers that recorded their every move, creating a detailed map of 57,604 distinct trip chains. The team did not just look at the big picture; they dissected the journey into its smallest parts. They separated the walking that happened at the start of a trip, known as access, from the walking at the end, known as egress, and the walking that happened in the middle when switching from one vehicle to another, known as transfer. By analyzing these specific segments alongside the types of vehicles used—such as cars, buses, trains, trams, and bicycles—the researchers could see patterns that were previously hidden. They found that intermodal trips, where a person uses at least two different non-walking modes of transport, made up only a small fraction of all trips, about 6.4 percent. Yet, within this small group, the behavior was far from random.

The study revealed that the order in which people use different modes of transport is not a matter of chance. Certain vehicles have a strong tendency to appear in specific spots within a journey. For instance, private cars almost always appear at the very beginning of a trip or at the very end, rarely in the middle. This suggests a clear pattern of behavior where people drive to a station and leave their car there, or drive from a station to their final destination, but they do not typically drive in the middle of a public transport journey. Conversely, active modes like bicycles and e-bikes showed much more variety, appearing at different points in the chain depending on the situation. The researchers also discovered that the type of public transport used dictates the walking experience. When a trip involved a train, the walking segments were consistently longer, both at the start and the end of the journey, compared to trips involving buses or trams. This is because train stations are often larger and set further back from the street, requiring a longer walk to reach the platform or the exit, whereas bus stops are usually right on the sidewalk.

The position of the walk within the trip also mattered significantly. People tended to walk longer distances when starting a journey from home or an activity location to catch their first vehicle than they did when walking from their last vehicle to their final destination. This suggests that when leaving, people are willing to cover more ground to secure their connection, perhaps because they have more time or because the starting point is less well-served by transport. However, when arriving at their destination, the walking distance was shorter, possibly because residential areas are generally closer to transport stops than workplaces or shops are. The walking that happened in the middle of a trip, between two vehicles, was different again. Its length was not determined by the purpose of the trip or the person's schedule, but almost entirely by the physical layout of the transport hubs. If a person had to switch from a bus to a train, or from a car to a tram, the distance they walked was dictated by how far apart those specific facilities were built.

These findings challenge the idea that all walking in a transport system is the same. The study shows that the effort a person is willing to make depends heavily on where they are in their journey and what vehicle they are using. The researchers found that the "last mile" problem is not a single, uniform challenge but a collection of different situations. A train station creates a different walking burden than a bus stop, and a trip starting at home creates a different walking pattern than a trip ending at home. The data suggests that to make intermodal travel more attractive and efficient, planners cannot rely on average numbers. They must understand that the walking experience is shaped by the specific combination of vehicles, the location of the trip, and the physical design of the transfer points. By recognizing these nuances, cities can design better connections that respect the actual behaviors and limits of the people who use them, making the transition between different modes of transport smoother and less burdensome.