The depreciation on the trucks used to deliver products to customers is a period cost. The depreciation on delivery trucks will be reported as an expense on the income statement in the period in which it occurs. It might be reported as part of Selling Expenses or as part of Selling, General and Administrative (SG&A) Expenses.
The depreciation on the trucks used to transport materials or work-in-process between the facilities of a manufacturer is a component of manufacturing overhead. In other words, the depreciation on trucks used in the manufacturing process is assigned to the goods produced rather than being expensed directly.