Is it possible to use a rapid transit-style system to carry light freight, such as parcels? So far no such system exists, and very few semi-relates systems exist (like pneumatic tubes for mail). But it remains an interesting potential technology, provided it is done right. Unfortunately, it is very easy to do it wrong through misunderstanding how freight or how rapid transit works. Therefore, advances in policy in this direction are good but should be done carefully.
Instead of giving people one big takeaway, I’m going to suggest a few good principles for this, motivated by both good and bad proposals.
1. Keep the tracks clear for maintenance at night
Germany’s minister of transport, CSU’s Andreas Scheuer, proposed running freight on the U-Bahn after hours. This is a terrible idea: regular nighttime closures are crucial for maintenance, and without them, maintenance costs go up and daytime reliability tanks. New York’s constant weekend service changes are the result of not shutting down overnight for maintenance nor being able to reliably single-track at nighttime headways. Berlin already runs overnight on weekends and does some daytime maintenance – “Ersatzverkehr mit Bussen” is one of the first ordinary German phrases I learned after moving here. Further encroachment on maintenance windows is not acceptable.
2. Use existing station infrastructure
The main cost in digging urban rail tunnels is the stations – boring tunnels between stations is a solved problem. This means that the main difficulty of urban rail freight is where freight gets on and off the trains. Loading and unloading container-size freight is impossible without massive station digs, all in expensive places. Having a freight car wait on a siding is not possible either – that interface between the customer and the freight railway relies on cheap land and time-insensitive shipping.
Most likely, shipping parcels by rapid transit requires using the existing stations and platforms. There is almost certainly no room at rush hour, when trains are sized to take up the entire platform interface to increase capacity. But in the daytime off-peak, there may be some room for using a portion of a subway station for parcels.
3. Keep up with passenger rail traffic
If freight trains can’t run at night, they have to slot on the same timetable as passenger trains. This isn’t a problem on the tracks – just add an EMU car loaded with parcels rather than passengers. But keeping dwell times under control is critical. Alert reader Mordy K. wrote about this, suggesting a “dynamic Rubik’s cube” that “shifts the packages around in 3D.” This is the real challenge: figure out how parcels get from the train to a designated spot on the platform or from the platform to a designated spot on the train during a 30-second dwell time.
4. Be aware of all interfaces between different systems
There are, at a minimum, five legs to a parcel trip in a city using rapid transit: origin to station, station to train, trip on train, train to station, station to destination. The boarding and alighting steps, so easy for the able-bodied passenger and even for the disabled passenger given rudimentary investment into accessibility, are difficult for a parcel of freight. Tossing a package from a train to the platform is not enough: the package needs to get to the surface for the final leg of the trip. A courier could carry it, but at a high cost – the courier’s modes of transportation for the surface legs, like the e-bike, are bad at getting down to the subway and back up, so the time and physical effort costs are high.
This in turn means that the rail transit freight system needs to be able to put parcels in a freight elevator. Elevators are not free, although they are rarely as expensive as in New York. The problem is that parcels can’t walk across the platform, so the elevator has to face the exact same place every time, which may run into construction difficulties.
5. Don’t wreck passenger rail service
Berlin runs some trains short, especially after hours. Usually the first train after the beginning of short train service is very crowded, because passenger service demand is still too high for a half-train at the typical density of daytime Berlin trains. (I say typical density because I have never seen a Berlin train as crowded as the busiest off-peak trains in Paris or New York, let alone their busiest peak trains.)
What this means is that in practice there isn’t that much space on the train for freight. Running trains every 5 minutes until later at night but then cordoning off half for freight may be feasible – right now headways rise to 10 minutes around 9 in the evening – but it’s still just a few evening and early night hours for delivery.
This principle is equally important at the stations: cordoning off parts of the platform for freight is fine, but only if it does not interfere with passenger capacity or circulation. This may further constrain where freight elevators go: whatever automated system gets parcels from the train to the elevator will have to cross passenger traffic at-grade, and driverless technology can do it but not cheaply or smoothly.
6. Aim to work with a wide range of goods
Pneumatic tube systems for mail work for mail, but modifying them for other goods isn’t trivial. In contrast, a parcel delivery system should aim to be broadly usable by many goods with a high ratio of value added to weight. Subtle differences are important at this level of detail: glass and china goods can’t be thrown on the floor, fresh food spoils if it’s left outside for too long, jewelry and electronics face a high risk of theft. The technology has to have adequate tracking, punctuality, defense from shocks, and so on.
7. Be aware of the competition
Delivery by rapid transit is not the only alternative to trucks for cross-city shipping. Delivery by drone is in active development, both surface drones and flying drones. Surface drones have good synergy with trains, since surface drones are slow and make better first- and last-mile connections. But flying drones are in direct competition, since they work well at a range of a few kilometers rather than a few hundreds of meters. Flying drones so far only work at extremely high value-to-weight ratios, but if they become more widespread, it’s useful to think of how urban rail can compete.