## 3 Methodology
### Research Approach  
(1) Pedestrian Trajectory Extraction:  
Data Source: Trajectory data, which includes longitude, latitude, time, altitude, and speed, was collected using GPS-enabled mobile terminals (Wristband, Smartwatch, phone, etc.) at a frequency of 5 s from four students at Shenzhen University. The participants were selected based on their daily commuting patterns within the Nanshan District of Shenzhen, China. Data Scope: The dataset spans a 3-month period (January-March 2023), covering 13 parcel lockers (PLCs) and key urban areas, including academic buildings, dormitories, and commercial zones. Each user contributed approximately 15-20 walking trajectories per week, resulting in a total of 1856 trajectories (mean length: 1.2 km per trajectory). Filtering Criteria: Walking trajectories were extracted by applying a speed threshold of 4-5 km/h (average pedestrian speed) [37]. Trajectories exceeding 5 km/h were discarded to exclude non-walking activities (e.g., cycling or vehicular movement). Figure 1a,b illustrate raw and filtered trajectories, respectively. At the same time, during the data filtering process, different traffic modes can also be incorporated based on speed thresholds. (2) Identifying Activity Hotspots:  
Hotspot Definition: Activity hotspots were defined as spatially aggregated regions [38] (radius: 50 m) where users stayed for \(\geq\)1 h (temporal threshold). This dual constraint (distance: \(L\) = 50 m; time: \(M\) = 720; 3600 s) ensured that hotspots reflected meaningful information. Figure 1: Pedestrian trajectory extraction. (**a**) Spatial–temporal trajectory; (**b**) Walk trajectory. Colored points represent trajectory points, with non-walking trajectories marked within the yellow halos. Validation: Hotspots were validated against ground-truth POIs (points of interest, e.g., cafeterias, libraries) using OpenStreetMap data. For instance, 82% of identified hotspots aligned with known high-activity zones (e.g., the university library). Data Volume: The initial dataset included 24 to 36 hotspots per user (e.g., User A had 24 hotspots). Following the filtering process, 2 to 5 consistent hotspots per user were kept for PLC selection. Figure 2a,b illustrate the identification of hotspots before and after clustering. (3) Activity Hotspot Screening: To facilitate en-route goods pick-up, the activity hotspot screening process initially establishes whether the hotspots in the chain include the delivery point. It then assesses whether the user's walking trajectory data represents their regular path and extracts the trajectory that includes the delivery point. Subsequently, it filters out previous hotspots and the spatiotemporal trajectory leading to the delivery point. The screening of activity hotspots before and after is depicted in Figure 3a,b. (4) Regular Activity Hotspot Selection: Selecting PLCs requires identifying the user's regular activity hotspot as the starting point for pick-up, as the previous hotspot location  
Figure 3: Activity hotspot screening. (**a**) Before activity hotspot screening; (**b**) After activity hotspot screening. The yellow halo indicates irregular path, while the blue halo represents calculated regular activity hotspot. Figure 2: Hhotspot identification. (**a**) Hotspots identified; (**b**) Hotspot location calculation. The blue circle indicates the active hotspot area, while the red point represents the calculated hotspot location. before the delivery point is unavailable. The selection considers temporal and spatial distances, using kernel density estimation to convert these distances into values for hotspot identification. The chosen hotspot is located at the light ring in Figure 4a. (5) Parcel Locker Selection: After identifying the regular activity hotspot, the parcel locker is chosen based on its proximity to both the activity hotspot and the delivery point. The selection process takes into account the distance and time, integrating the weight, volume, and urgency restrictions of the express delivery into the decision-making.