Final answer:
The first sign drivers typically see when approaching a highway-rail intersection is an RXR round sign on a yellow background, which alerts them to the presence of a railroad crossing.
Step-by-step explanation:
When approaching a highway-rail intersection, the first sign drivers usually see is an RXR round sign on a yellow background. This sign is critical for driver and pedestrian safety, as it warns of the approach to a railroad crossing, alerting drivers to slow down and prepare to stop if necessary. Recognizing and understanding such common hazard signs help ensure that both drivers and pedestrians navigate traffic safely, reducing the likelihood of accidents at such intersections.