## 5 Experiments
### Experimental Evaluation
#### 5.3.3 Custom Environments  
We compare this to a small number of handcrafted layouts (c.f., Figure 8). In contrast to the random environments, navigation within these configurations is restricted by walls, which consequently facilitates navigation conflicts and congestion. Additionally, these environments are intentionally structured in specific ways to simulate certain general characteristics. **Custom 1**: In this environment the navigation graph is very broad. Distances between the stations are relatively short and navigation is possible along many paths in parallel. The input storages are located on the left side, while the output storage is located on the right. In order to navigate from the output storage (common drop-off location) to the input storage (common pick-up location), the vehicles need to pass the assembly stations (common pick-up locations). The idle positions are located centrally between the assembly stations. From these last two conditions, we expect transports to prioritise the transports from the assembly stations to the output storage for high vehicle utilisations. The general structure is similar to the _Custom_ 1 environment. Only the assembly stations are located along two long corridors, such that traffic will concentrate along there. The idle positions are again located between the assembly stations. Here, we again assume that vehicles will prioritise transports originating from the assembly stations. Here, the emphasis on navigation conflicts is increased slightly, which might give an advantage to the LSAP approach according to the hypothesis postulated in Section 2.3. The environment is very similar to _Custom_ 2, but here the input storage are located between the assembly stations and the output storage. This way, we assume that transports, especially those facilitating reassignment, will prioritise the delivery of input parts and thus lead to a larger assembly utilisation and throughput. Thus, we would expect a larger advantage of the reassignment-based dispatching. The experiment variations regarding the target values for P/T ratio and vehicle utilisation correspond to those defined before (c.f., Section 5.1). The evaluated run configurations and the corresponding results can be found in Table 4.  
General Observations  
As we also noticed before in Section 5.3.2, we received a strong relationship between the utilisation of the vehicle fleet and the output performance in terms of throughput and efficiency. Here too, other things being equal, a higher vehicle utilisation results in a decrease in throughput and an increase in efficiency (higher travel efficiency, lower throughput effort). For the Custom 1 layout we notice that LSAP achieves the best performance for low P/T ratios independent of the vehicle utilisation (7a, 7b). STTF method scores significantly better than the others with configuration 8b, featuring high P/T ratio and high vehicle utilisation. The SMP method scores significantly worse than the others with configurations 7a, 8a, and 8b. Regarding the total travelled distance, the SMP method scores best for all four configurations. As before, STTF scores worst on this metric. As to the efficiency-related scores we note that, as before, STTF achieves significantly lowest values for most configurations (7a, 7b, 8a), the only exception being configuration 8b (high P/T ratio, high  
Figure 8: Custom environments. Light blue coloured areas represent input/output storage. Greyish areas represent assembly stations. Purple areas/lines represent walls. Thin grey dots and lines indicate the navigation graph (nodes and edges). vehicle utilisation), where it scores best. The LSAP method scores significantly better at both scores with configurations 7a, 7b (low P/T ratio). With configuration 8a, LSAP outperforms SMP only at the throughput effort, but not at the travel efficiency. The Custom 2 layout indicates the best throughput performance with the STTF method for configurations 9a, 10a, and 10b, but worst performance for configuration 9b.