A number of shipping lines operating on a certain route, which agree on a common policy regarding the conditions under which goods are to be carried

The correct term for a group of shipping lines that agree on a common policy regarding the conditions under which goods are to be carried is a "conference." A conference is a group of shipping lines that come together to set standards and establish guidelines for the transportation of goods on a particular route. By working together, the conference members can ensure that they are providing a consistent level of service to their customers, as well as agreeing on pricing and other important terms. While some people might use terms like "cartel," "syndicate," or "trust" to describe this kind of arrangement, those terms are generally associated with illegal or unethical practices like price-fixing, market manipulation, or collusion. In contrast, a conference is a legitimate and legal arrangement that allows shipping lines to work together to provide better service to their customers while maintaining healthy competition within the industry.