A refrigerated truck semi-trailer, also called as freezer semitrailer, reefer truck semitrailer. It is a specialized type of vehicle used for transporting perishable goods at controlled temperatures. The main purpose of a refrigerated truck semi-trailer can be summarized into four key points:
1. Transporting Fresh Produce: One of the primary purposes of a refrigerated truck semi-trailer is to transport fresh produce such as fruits, vegetables, and dairy products. These perishable goods require specific temperature conditions to prevent spoilage during transit. 
2. Food Distribution: Refrigerated truck semi-trailers are commonly used in the food distribution industry to transport a wide range of perishable items including meat, seafood, and frozen foods. The temperature-controlled compartments of the truck allow for the safe transportation of these products over long distances without compromising their quality or safety.
3. Pharmaceuticals and Biomedical Products: Another important use of refrigerated truck semi-trailers is in the transportation of pharmaceuticals and biomedical products that require strict temperature control. 
In conclusion, the main purpose of a refrigerated truck semi-trailer is to provide a reliable and efficient means of transporting perishable goods at controlled temperatures, ensuring that these products remain fresh and safe throughout the journey.