What does the letter combination 'RR' on the pavement indicate?

The letter combination 'RR' painted on the pavement signifies a railroad crossing. This marking is intended to alert drivers to an upcoming railroad crossing where trains may be present. It serves as a warning, emphasizing the need for extra caution while approaching this area. The presence of this marking is crucial for safety, as it prepares drivers to look out for potential oncoming trains, ensuring they slow down and check for trains before proceeding.

In contrast, other options do not correctly represent the meaning of 'RR.' A stop sign ahead would typically be indicated by a stop sign itself rather than pavement markings. A bike lane would be marked with bike symbols or specific lane markings but would not utilize 'RR.' Additionally, a school zone is usually designated with signs and sometimes painted markings indicating reduced speed but does not involve the 'RR' designation. Therefore, 'RR' is explicitly associated with railroad crossings to enhance road safety.