Urban Logistics: When the tugger train honks twice

The history of tugger trains begins with milk, or at least that is one explanation. Back when there were no refrigerators, when milk was still a perishable commodity, milkmen and milkwomen clattered around to homes with their carts, taking empty milk bottles with them and putting new ones in front of the door. Even today, tugger trains are still known as, "milk run systems". Another plausible origin story is tied to the fact that milk production facilities were supplied by trucks that had previously made their rounds at dairies and farms. The outcome is the same whichever story you choose to accept: A transport vehicle utilizes a central route to save time and resources.

Thus, it comes as no surprise that tugger trains today are closely linked to lean management, an efficient organization in a value-added chain. "Anyone looking at ‘lean’ solutions will eventually end up with tugger trains," notes Herbert Fischer, the head of Tugger Train Sales & Consultancy at STILL. In a production facility, this is what you would see: A relatively small vehicle pulling several load carriers in a row and heading from the warehouse to the production hall.

KION brand STILL has been spending a lot of time developing tugger trains and getting its own patents. Why? Because apart from the basic concept, there are several potential ways to implement the concept. "The most obvious variant is to bolt the drawbar and wheels to a load carrier," says Fischer. Yet, what at first glance appears to be efficient and simple, quickly becomes impractical when maneuvering: To gain access to the trailers, they must be uncoupled on each side every time. Additionally, these constructions are not especially nimble nor robust. It is why STILL prefers a push-in concept where loads can be pushed in and out from each side in specially manufactured, heavy-duty frames.

With a little imagination, the approach could be applied to an urban area and the last mile where a tugger train - or a tugger train-like vehicle - is utilized in densely populated areas, driving to a central location. From there, the packages are delivered to your front door. An added feature involves automating at least one of the two steps: either the tugger train, or the delivery itself. Since tugger trains only commute between the same central locations anyway, automation would be easier than it would be with a free-moving vehicle. "I can even imagine a scenario where residents know they can head to their front doors to pick up their goods when they hear a certain tone from the vehicle and then sending the tugger train back on its way by simply pushing a button," says Fischer. And perhaps before too long, you might be hearing people say, "When the tugger train honks twice". You must admit that the idea has its appeal.

It is also conceivable that delivery to your front door could be automated using small driverless transport vehicles that collect packages from the tugger train and then take the shortest route from the central transshipment point to your front door. Alternatively, the destination could be a packing station or similar decentralized locations. "We're really talking about the last stretch of the route," says Fischer. "The automated vehicle could then handle a larger volume all at once like a swarm." In warehouses, this is already technically possible and STILL has developed and implemented this very solution. Fischer is convinced that the trend will pick up with customers. Driverless transport systems are one of the hot buttons in the intralogistics industry.

Noe van Bergen who is the head of Automated Solutions at STILL, is convinced the approach using driverless transport systems which control a specific destination from a central transshipment hub to be applicable to urban logistics.

For the warehouse, developers from every technical area at KION Group are working to ensure that the vehicles also function smoothly when humans are on the road at the same time. van Bergen hopes it will also have positive effects because the automotive industry is also conducting similar research.

"We can do a lot; we have spacers and GPS, but the biggest ‘unknown’ is still the human being,", admits Fischer, explaining that humans are much more difficult to calculate than any vehicle. It is precisely these challenges that everyone who wants to succeed in the ‘last mile’ will have to face. There is also the question of precision: "If we assume that the transport vehicle will end up in front of a row of apartments with 60 address plates, then it needs to be able to locate the right mailbox," van Bergen says. These are the same issues that KION Group engineers must figure out, including picking the exact package needed from among several packages and storing it in the correct place. Another question that comes up: what happens when a vehicle has a problem? In the warehouse, an employee can run over and fix the problem, but does it also work if the package delivery vehicle has to stop at the curb because it can’t get up?

Curbs are a challenge for the delivery driver during delivery. After all, the physical effort involved in walking from a car to the recipient’s door is quite considerable and stressful. There are warehouse solutions that have been tested and have been in use for some time: Linde Material Handling’s CiTi truck is a good example, which is a pallet truck. In the warehouse, pallet trucks with their two long tines are useful wherever goods must be moved by an employee over a shorter distance in a confined space at ground level. They are small, maneuverable and can be pushed or pulled. These are exactly the strengths pallet trucks can put into play in the last mile; however, pulling and pushing on cobblestones as well as heaving over heels and ramps is still a physical challenge. "The CiTi truck has an electric drive, which is a great benefit, and it can handle sidewalks," explains Markus Schmermund, a vice president of Automation & Intralogistics Solutions at Linde MH, another KION brand.

It makes it an ideal vehicle for transporting goods from the delivery van to the recipient’s door right now. Think of deliveries for retail or for restaurants, up to 500 kgs (1,100 lbs.) of goods can be stacked on pallets on the CiTi Truck. "In the daily delivery, industrial trucks are most likely already being used on these types of routes, but not always on the right ones," guesses Schmermund. Simple variations that do not deploy electric drive offer hardly any real physical relief, while large, heavy warehouse trucks are simply not made for cobblestones, potholes and curbs he explains. "There are high-grade electronic components in these devices that would be damaged under these conditions."

In addition, there is the noise level generated by heavy equipment. "When you think of the challenges involving city deliveries, noise is definitely one of them," says Schmermund. "Nobody wants to be driven from their beds by delivery traffic at five in the morning." Linde’s CiTi truck, however, runs on special noise reduction rollers.

Thus, there is much to be learned from intralogistics and directly applied to urban logistics. On the one hand it is the very specific applications such as Linde’s CiTi Truck, or in a broader sense, the expertise that KION Group's intralogistics specialists have collected over the last several years in tugger trains and automation. "No matter what, it's a very exciting field," beams Fischer. Automation, right down to autonomous swarming, bundled transports and the interfaces between humans and machines. Each of these topics is certain to become critical for both intralogistics and urban logistics before too long. Even if it is more likely to be possible to adapt the environment on a production site so that delivery vehicles can cope with it. On the other hand, why not see this happen in cities? Perhaps then tugger trains will arrive at your house and honk twice.

Part 4 of the "Urban Logistics" series: the new retail reality: Dematic's micro fulfillment solution.

Markus Schmermund about solutions that intralogistics may have for the last mile.