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Autonomous mobile lockers for city logistics

Autonomous mobile lockers
Toyota's e-Palette concept vehicle. Source: Toyota

In this study, Autonomous Mobile Lockers (AMLs) are introduced into the current city logistics network. The proposed system consists of couriers working with AMLs that visit the couriers in the field and transfer parcels to and from the depot.

Couriers can continue their tours without having to make hourly returns to the depot. At the same time, AMLs can enlarge the coverage of depot and reduce the number of depots, saving on depot rent.

In addition, a high frequency of collection and delivery by AML can shorten the maximum delivery time of parcels within the city.

This PhD Project will propose a mathematical model to determine the best tours of the AMLs, together with the number of depots required. This new model involves solving a two-echelon Location Routing Problem (2E-LRP).

Efficient solution methods will be developed for both the day-to-day problem and within-day plan modifications due to demand variation and delays. Finally, a sensitivity analysis on some important design parameters will be conducted.


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Project background

With the development and increasing popularity of e-commerce, the demands on logistics operations have also increased. This has resulted in serious environmental problems such as traffic congestion, air and noise pollution, increasing energy use, and global warming.

In the United States, 28.5% of total greenhouse gas (GHG) emissions is accounted for by freight transportation. The United Nations has identified environmental sustainability as one of their primary concerns. Addressing these concerns, some governments are imposing traffic restrictions on access to city centres for certain types of trucks. For example, Xian, Zhengzhou and other cities in China have banned trucks from entering the metropolitan area since November 2018. This means that logistics companies need to use smaller vehicles in the city centre, increasing the cost of transport for logistics enterprises and the chances of increasing traffic congestion.

To reduce environmental pollution and relieve congestion, advanced planning and routing systems, cooperative transport systems, load factor control and most importantly from the point of view of this study, Autonomous Mobile Lockers (AMLs) can be deployed.

Fixed-time windows are commonly included in parcel pickup and delivery operating models, whereby shipments are forced to be picked up or delivered at certain times, determining when shipments will arrive or depart the hubs.

This results in traffic congestion, especially during rush hours. In order to deal with peaks in shipments, operational capacity needs to be increased. Since the volume of shipments continues to rise, the network needs to operate new warehouses (depots) and expand hubs, locations that are difficult to find in large cities.

However, resource utilisation is low during off-peak periods, so techniques need to be found to spread the peak. At the same time, fixed-time windows also lead to long transit times in pickup and delivery, causing problems for same-day delivery.

Due to the development of e-commerce, customers have high expectations from the logistics industry in relation to service quality, shipment safety, timing, and cost. To manage this growth, logistics companies need to allocate limited resources efficiently to reduce operational costs and delivery times to meet customer expectations for rapid delivery. Better scheduling in distribution systems can shorten customer waiting times for deliveries and significantly improve customer experience and satisfaction.

A good vehicle routing and scheduling model can reduce the number of trucks required, the vehicle-kilometres travelled, and the operating costs by 11% to 16%. The selection of appropriate vehicle size combined with efficient vehicle routing can bring about the desired economic and environmental benefits.

Therefore, in this study, we introduce a new pickup and delivery technology, called the Autonomous Mobile Locker (AML), into the existing city logistics network. The AML can help us optimise network planning, increase the coverage of the depot, save facility rent cost, shorten transit time for same-city shipments and increase the utilisation of staff and equipment.

Project objectives

  1. Introduction of a new pickup and delivery technology, the Autonomous Mobile Locker (AML), with the objective of saving the logistics service provider cost and time.
  2. AMLs are deployed to connect depots and couriers, helping expand the coverage of depots and allowing their number to be reduced. AMLs are relatively cheap compared to other facilities, so overall costs can be reduced.
  3. Multi-echelon location routing problems will be formulated for the AMLs and solved for both day-to-day planning and for within-day adaptation to demand variation and unexpected delays. Scaling up the problem for realistic scenarios will require the development of innovative heuristics.
  4. The use of AMLs to facilitate same-day delivery within a city will be explored. This may involve AMLs connecting couriers in the field or feeder vehicles linking depots on routes to and from the hub. Allowing parcel transfers for same-day delivery to bypass the depots or the hub will reduce the peak workloads in the depots and the hub, again saving time and cost.
  5. The use of AMLs, which will be electrically powered, will have a beneficial impact on the city environment by reducing traffic congestion, noise and emissions when compared to the conventional alternative. There will be an attempt to quantify this benefit for realistic scenarios.

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