What is“ contract carriers”?

What is“ contract carriers”?
【正确答案】：Individual contracts may be arranged between transportation users and carriers. With the formal agreement, the transportation company becomes a contract carrier.
【题目解析】：该题目素材选自L14。contract carriers意为“契约承运人”。托运人和承运人之间可签订独立的合同。有了正式合同，运输公司就成为契约承运人。