When using another railroad's signals, what must you do to determine how to proceed?

Answer: B — Use BNSF's special instructions for their signals

Using another railroad's signals requires following specific protocols that they have in place. When encountering signals from a different railroad, such as BNSF, it is essential to consult that railroad's special instructions. These instructions are tailored to their operational rules and signal configurations, ensuring safety and compliance with their unique protocols. Different railroads might have varying signaling systems, and assumptions based on one’s own railroad’s signal rules could lead to misinterpretation and potentially hazardous situations. By utilizing the special instructions, a conductor can accurately interpret the signals based on the local railroad’s established practices, thus ensuring safe and efficient movement through their territory.