Business inventories rose 0.4% in September, while sales increased 0.6%, the Commerce Department said Wednesday.
The uptick of goods unsold at factories, retailers and wholesalers followed a 0.3% gain in August that was higher than initially reported.
When sales are growing, it usually means trucking is seeing additional demand to deliver goods and restock shelves.
Higher inventories mean goods are not being sold at a rapid pace, which could lower demand for trucking services.