# Hub Airport End-Around Taxiway Construction Planning Development: A Review
## 3 End-Around Taxiways (EATs) around the World
### End-Around Taxivay Classification
At airports with a single EAT, such as ATL, the EAT can also be used as a BAT when the runway direction changes. This allows taxiing aircraft to pass safely behind departing ones, albeit at a longer taxi distance and time. Nevertheless, as other EAT configurations offer further detour distance reduction, BAT implementations are becoming less frequent in large airport designs. (b) REAT (Runway End-Around Taxiway) mode is located in front of the departing runway end and safety zone, also known as \"far-end of departing runway around taxiway\". It takes into account factors such as the climb surface and ILS lighting system [6]. REAT is a well-established and safe mode that is currently in use at airports like ATL, DFW, and DTW. Figure 9 shows the example of typical REAT operation. Figure 8: Example of typical BAT operation. REAT is the most commonly utilized type, often referred to as an EAT in the academic literature. It is worth noting that taxiways have other uses besides REATs (as previously mentioned). To avoid confusion, this article will refer to this type of maneuver as REAT. (c) SAT mode: Start-Around Taxiway, also known as \"near-end of landing runway around taxiway\", refers to taxing around before the runway entrance, allowing normal aircraft landings. Figure 10 shows the example of typical SAT operation. Compared with REAT and BAT, the construction of SAT needs to consider more factors such as approach surface, lighting, and navigation. SAT can fulfill the functions of both REAT and BAT, making it a versatile and obstacle-free taxiway option. In the case of a dual parallel runway configuration, the function of the two runways is relatively fixed, with the inner runway only used for takeoff. However, in the case of a dual-terminal area, such as the M-shaped taxiway mode, the future terminal area may involve conversion, a runway previously used for takeoff will be used for landing, or the function of parallel runways is undecided, which requires the ATC to determine the division of labor for takeoff and landing based on meteorology and streamlining [63; 64; 65; 66]. In this case, EAT needs to consider the impact on the approaching aircraft, as well as the approach surface and related ILS and lighting systems. Initially, considering the effect of SAT on the approaching aircraft, the FAA did not recommend the SAT, but notably, the 2023 draft AC 150/5300-13B--Airport Design provides design guidance for EATs under the approach surface [67]. In practice, the SAT operating mode has been successfully implemented in both PEK and KWE. Its adaptability in runway and flow conversions allows it to be seamlessly integrated as an EAT. Regardless of runway usage or flow selection, SAT can be employed without hesitation. Truly a multi-functional taxiway, SAT simultaneously fulfills the roles of EAT, BAT, and SAT, essentially operating as an unrestricted EAT. ATC can direct pilots to the most convenient route, ensuring swift arrival at the target terminal without delay  
Figure 10: Example of typical SAT operation. Figure 9: Example of typical REAT operation. or additional instructions [36; 68; 69]. SAT's implementation has reduced ATC stress and instructions, gaining popularity among controllers and achieving high utilization rates.