## 2 Related Work
### Facility Location Problems
In their simulation, they measure the overall CO\({}_{2}\) emissions from deliveries and pickups and find a positive effect in most instances, with up to 40% CO\({}_{2}\) savings using APLs. The authors of [41] evaluate the impact of APLs on reducing several pollutants. They study the effect in New York City and use bike-sharing stations as potential APL locations. Furthermore, they offer a comprehensive overview of research on emissions involving APLs. Even though all of these studies consider emissions, e.g., [42; 43; 44; 45; 46; 47], only some include customer pickups explicitly [48; 49; 50; 51]. The results presented by [47] indicate the substantial benefits from implementing APLs for both the operator and the municipality. The overall VKT were cut by 90.9%, rendering nearly 80% of the vehicle fleet unnecessary. The model architecture comprises three key components: (i) customer location, specifying whether the customer's house is in an urban or extra-urban area; (ii) average distance needed to reach the APLs for customers; and (iii) average distance between two APLs (density of APLs). The authors incorporated emission factors within DD and APLs based on interviews with major logistics operators in Italy. The model does not include detailed locations of customers and APLs or algorithms to solve VRP instances. Ref. [48] suggests that the environmental benefits of an APL remain valid for the community, including couriers and customers, as long as the distance a customer must travel by car to reach the APL is within 0.94 km in urban areas and 6 km in rural areas. On the selected simulation day, five vehicles executed 70 delivery stops for DD in a given area from 11:00 a.m. to 4:30 p.m. For a comparison with an APL network for the same area, the estimation focused on the number of cars involved in collecting parcels from the APLs. The simulation considered only the car option among various modes of transport to and from the APLs, i.e., pedestrian movements, cycling, and public transport were not an integral part of the model. Refs. [49; 50]'s findings accurately represent the daily operations of a carrier serving West Sussex, extrapolating over a year with 62,400 deliveries. The authors look at a different process, where customers only pick up parcels at so called collection-and-delivery points (CDPs), in case that they were not at home when visited by a vehicle of the carrier on a DD tour. The most significant savings in emissions, with a 44% reduction, occurred when local post offices were utilized as CDPs. This outcome was based on the assumption that 50% of the deliveries failed initially, and 30% of those unsuccessful deliveries resulted in consumers collecting their packages from the carrier's depot (87% by car). Emissions from both the carrier and household were quantified for different CDP configurations and compared to DD visiting customers a second or even a third or fourth time. The results showed that CDP delivery systems led to a reduction in emissions ranging from 48% to 58% compared to the traditional approach of only DD. The findings outlined in [51] conducted an evaluation of the freight component in failed deliveries. It was observed that the additional CO2 emitted during the second delivery attempt resulted in an increase in emissions per drop, ranging from 9% to 75%. The predominant emissions (85% to 95%) from a failed DD result not from the subsequent van re-delivery but from the individual customer traveling to collect a missed delivery from the carrier's local depot. Various CDPs (supermarkets, post offices, and railway stations) were identified as effective at reducing the environmental impact of this personal travel. Notably, post offices yielded the most significant savings in this context, accounting for only 13% of the CO2 produced in comparison to a collection by car directly from a local depot. Again, the presented research focuses solely on potential CO2 savings for failed deliveries.