Intermodal Routes and Why It’s Hard to Find Them
Intermodal trips look like a saving grace in getting people out of their cars. Aurelija Petrauskytė-Latakė — Trafi’s Lead Product Manager for Routing — dispels the complex nature of intermodality and explains why people find it challenging to rely upon it.
Mechanics of Human Mobility Decisions
Imagine that you are having coffee with a friend near Potsdamer Platz in Berlin on a lovely Saturday morning. Your friend gets an idea to visit the Zoo, and you don’t hesitate to agree. Now, if you were Anna, a Berliner through-and-through, you would walk. It’s 46 minutes, a beautiful route, and she enjoys a pleasant stroll while catching up on her podcasts. However, if you were Peter, an ex-pat, you would prefer convenience while being very price sensitive. In other words, you would take a bus. Would getting caught in the rain change anything? Anna most likely would immediately jump into a shared car and go back home. For Peter, however, nothing would change: it’s price over comfort pretty much always, and it’s charming when it rains.
These are typical mobility deliberations we all make every single day. What we are considering — taking a bus, car, or walking — are routes from point A to point B. Every route has an origin, a destination, a mobility mode, a path, and a cost. Anna doesn’t mind the physical cost of walking because she finds standing on a platform or inside a train annoying. Peter, however, is willing to pay for the convenience of public transport above the physical toll of walking. You, however, would likely have a different attitude. We all are different people with distinct preferences in disparate situations.
The takeaway: no route is absolutely right for everyone. Every option we take is a tradeoff against the existing alternatives.
Mechanics of Trip Planners
Say that Anna, Peter, and you are relying on the same trip planner to find your mobility options. Well, then the routing software that powers any trip planner would have to know, accept, and adhere to your differences and return a set of mobility options that would make sense specifically to you and your situation. Honestly, every trip planner faces a challenge to achieve that.
There is a solution, though: every one of us, including Anna, Peter and you, consider wait time, trip price, duration, distance, etc. What makes us all different are the distinct values we assign to shared preferences: Anna is more tolerant of walking, and Peter is more tolerant of public transport. I, for example, maybe am more tolerant of paying for ride-hailing. Keep in mind that these tolerance levels also are sensitive to context: whether it’s raining or if it’s rush hour, whether you’re carrying grocery bags or just running late — we all tend to reconsider our usual choices if the situation changes. Routing software would have to start exactly here: by embedding this shared set of preferences and assigning tolerance levels specific to people, cities, and even context.
In other words, trip planners have to consider our shared preferences and return a list of routes that make sense to our tolerance levels in any given situation.
Mechanics of Intermodal Routing
Anna and Peter’s options look like a walk in the park in comparison with intermodal routes, e.g., combining a shared mobility option with a public transport one. Imagine that for that trip to Berlin’s Zoo; you decide to take the intermodal route recommended by your trip planner: a TIER kick scooter with a transfer to U-Bahn №2.
What follows is the actual sequence of actions you would be required to perform in an intermodal trip. First, your find a scooter, walk to the scooter, unlock the scooter, put on a helmet, ride the scooter from Potsdamer Platz to Mendelssohn-Bartholdy-Park station for 5 minutes, confirm that you can lock the scooter, take off the helmet, lock the scooter, enter the station and find the platform, wait 6 minutes, transfer to U-Bahn №2, ride five stops for ten more minutes, and complete your last mile on foot.
That’s 23 minutes and around 5 euros. Slower than car-sharing or even a bus but, probably, more convenient than walking. But for this trip to even be recommended, a trip planner has to perform some severe behind-the-scenes calculations:
1. Evaluate the amount of effort you are willing to invest in this route, i.e., tolerance limit to walking, tolerance limit to driving yourself, tolerance to switch from a self-driven mode to a mode where you are driven, tolerance to wait for a transfer, etc.
2. Evaluate mobility service availability, i.e., inquire all integrated shared and public mobility providers in real-time about their available supply, so that you would be able to unlock a kick scooter to start the trip, and a transfer to U-Bahn at your connection point without the necessity to wait for a long time,
3. Predict upfront, i.e., combining the availability and your tolerance levels, calculate how far into the future this trip can be guaranteed, as the scooter supply changes constantly, they cannot be reserved indefinitely. At the same time, U-Bahn №2 does run on a schedule, but it does get disrupted sometimes, and you still have to make your connection at a specific time.
In other words, a trip planner has to recommend intermodal routes that make sense: provide options that show a tradeoff between price, the effort needed, and time saved. But even then, one person will find paying 5 euros for a 23-minute trip outrageous while another would be less concerned about price. Moreover, people are also less likely to consider taking intermodal routes where they are not guaranteed supply at transfer stations.
So, Is Our Future — Intermodal?
One of the points that tend to get lost in the whole debate about the future of urban mobility is the cognitive complexity of intermodal routes. As we’ve discussed before, people calculate tradeoffs. Risks of not finding a kick scooter, riding on unknown streets amid the car traffic, the possibility of missing your U-Bahn connection — it all adds up to an apparent reason why Anna and Peter will mostly prefer sticking to their regularly scheduled options in the upcoming future.
Nevertheless, for most people, sticking only to scarce public transport or private cars is not an answer either. We must increase the connectivity of the whole urban mobility network. Intermodal trips seem to be a legitimate way to get there. One immediate example is urban park & ride systems that allow commuters to leave their cars and switch to public transport or micro-mobility.
To put a finer point here: intermodal routes are already being suggested. In Berlin, Jelbi — a city-led MaaS platform — recommends taking at least one shared mobility combination with public transport in every tenth route search request. However, guaranteeing intermodality is still very complex: these routes have to deal with far more variables than distinctly public transport or shared mobility ones.
One can only hope that intermodal variability can be handled by an abundance of micro-mobility supply soon. Until then, it’s only natural that for regular people, intermodality is rarely the preferred option.
–Aurelija Petrauskytė-Latakė,
Lead Product Manager for Routing
