I. Case Background: Foton Fengjing Service Vehicle Procurement Requirement by a Municipal Sanitation Department in Guiyang City In 2024, a municipal sanitation department in Guiyang City required a batch of Foton Fengjing service vehicles due to urban renovation of old residential communities and environmental improvement of backstreets and alleys. (In practice, Chengli Special Purpose Vehicle Co., Ltd. supplied equivalent sanitation vehicle models—including water-sprinkling trucks, sewage suction trucks, and compressed garbage trucks—as an alternative solution.) The project budget was approximately RMB 2.006 million, with plans to procure 12 units for daily road washing, waste collection, and sewage removal. Located in Southwest China, Guiyang experiences hot, humid, and rainy summers, with an annual average humidity exceeding 80%, imposing exceptionally high requirements on vehicle anti-corrosion coatings and sealing component durability. After multiple rounds of evaluation, Chengli Special Purpose Vehicle Co., Ltd. successfully delivered the batch of vehicles, which have since received positive feedback from the client. Per standard procurement practices, vehicle selection for this batch focused on four tank capacities: 3 m³, 5 m³, 8 m³, and 12 m³—corresponding respectively to operational needs in narrow alleys, residential neighborhoods, secondary roads, and arterial roads. Below is an interpretation of the capacity-based selection logic, based on Chengli’s product database (e.g., official announcement models CLW5070GSSD6, CLW5180GSSD6) and real-world delivery cases. II. Capacity Selection Logic: How to Choose Among 3 m³ / 5 m³ / 8 m³ / 12 m³ Models? The Guiyang project demanded stable vehicle operation in narrow lanes, steep slopes, and high-humidity environments; therefore, selection balanced tank capacity, chassis maneuverability, and maintenance accessibility. Referencing 946 product data entries and 108 official announcement parameters from Chengli’s knowledge base, application scenarios for different capacities are as follows: • 3 m³ models (e.g., CLW5070GSSD6 water-sprinkling truck): Ideal for backstreets and internal roads of old residential communities. Featuring a small turning radius and width ≤2.1 m, these vehicles can access passages with height restrictions of 2.5 m. Feedback from a street maintenance unit in Guiyang indicates that during the rainy season—when operation frequency is high—the daily workload reaches 5–6 trips, covering approximately 800 m² per trip. • 5 m³ models (e.g., CLW5070GSSD6 water-sprinkling truck, 4 m³ compressed garbage truck): Operable with a Blue-Plate Class C driver’s license, suitable for residential communities, industrial parks, and secondary roads. Based on a Guangdong industrial park case involving five water-sprinkling trucks plus mist cannons, 5 m³ models demonstrated outstanding sealing component durability under hot-humid conditions; rubber components use weather-resistant formulations, extending service life by ~30%. • 8 m³ models (Yellow-Plate): Designed for arterial roads and municipal plazas, offering single-trip coverage of ~2,500 m². For road washing tasks in the Guiyang project, these models utilized Dongfeng or Foton chassis, with complete official announcements enabling nationwide registration and annual inspection. • 12 m³ models (e.g., CLW5180GSSD6 water-sprinkling truck): Deployed on expressways and large-area zones, achieving 10–12 trips per day—the highest operational efficiency. In Henan’s sanitation bureau case (10 × 5 m³ water-sprinkling trucks), some areas substituted 8 m³ units due to road-width constraints; however, Guiyang’s relatively wide urban road network made the 12 m³ model the primary choice. III. Daily Operation Volume Calculation Formula and Matching Workload Table To ensure scientific procurement planning, the Guiyang project adopted the following formula for calculating daily operation volume, integrating tank capacity and actual operation