Which type of order remains effective until canceled or fulfilled?

The correct answer is Bulletin Order, as it is a type of order that is designed to stay in effect until it is specifically canceled or has been fulfilled. Bulletin Orders typically provide important and lasting directives that can be relevant over an extended period of time, often pertaining to rules, procedures, or guidelines that are crucial for the operation of railroads and locomotive operations.

In contrast, other types of orders such as General Orders and General Notices may have specific expiration times or may be updated frequently, thus requiring regular review and reissuance. Operational Notices generally provide information that is short-term in nature and may change frequently to address immediate needs or updates within the operational environment. These other orders do not carry the same enduring status as Bulletin Orders, which maintain their authority until a deliberate action is taken to cancel or complete them.