Final answer:
Pennant-shaped road signs indicate a No Passing Zone, serving to enhance driver awareness and maintain road safety in potentially hazardous areas where visibility is restricted.
Step-by-step explanation:
Pennant-shaped signs on the road primarily indicate a No Passing Zone. These signs are specially designed to capture the attention of drivers and convey important traffic rules that enhance safety. Unlike symbols that may have varied meanings when used out of context or in different cultural settings, traffic signs have a specific purpose to ensure the smooth flow and safety of all road users. A pennant, being an uncommon shape among road signs, stands out and signifies that drivers should not pass other vehicles in areas where it may be unsafe to do so, such as where visibility is limited.