What sign may be used on tracks adjacent to a track requiring protection with a white background?

The correct answer identifies the Diverging Approach Speed Limit Sign as the appropriate sign that may be used on tracks adjacent to a track requiring protection with a white background. This is significant because the Diverging Approach Speed Limit Sign serves as a warning to trains that they are approaching a divergence where speed may need to be reduced. The white background indicates a specific kind of operational instruction within the context of NORAC rules.

Using a sign with a white background is intentional, as it denotes that the sign is providing guidance on speed restrictions or operational requirements that are vital for ensuring safety during transition areas on the track. The Diverging Approach Speed Limit Sign specifically alerts train operators earlier in the approach to help maintain a safe operation as they prepare for potential track changes or diverging routes.

This aspect of the sign aligns directly with the need for safety and operational effectiveness in areas close to tracks that require extra protection measures. Other types of signs listed, such as the Approach Speed Limit Sign or the Resume Speed Sign, do not accurately fit the criteria for use in such protective circumstances, and the Signal Indication Sign primarily conveys a different category of information related to signaling rather than speed restrictions adjacent to protected tracks.