Weight allowance is a term used in the shipping industry to refer to the maximum amount of weight that can be loaded onto a vehicle. The two crossword solutions, TRET and TARE, are abbreviations for two different types of weight allowance. TRET stands for 'TARE Residual Empty Truck' and is the weight of an empty truck before any cargo is loaded. TARE stands for 'TARE Allowance' and is the amount of weight that can be added to the truck after the TRET has been subtracted.