When approaching a railroad crossing, at what distance should a bus stop?

The appropriate distance for a bus to stop when approaching a railroad crossing is 15 to 50 feet. This range is specifically designed to ensure the safety of the bus passengers while providing enough visibility for the driver to assess whether it is safe to proceed or not. Stopping within this distance allows the driver to adequately see any oncoming trains, which is crucial for preventing accidents at crossings.

Stopping too far from the crossing could impair the driver's ability to gauge the situation effectively, while stopping closer than 15 feet might put the bus in a hazardous position where it's too close to the train tracks. Therefore, the 15 to 50 feet range balances safety and visibility, making it the correct answer in this context.