What is the significance of the "85th percentile speed" in traffic management?

The significance of the "85th percentile speed" in traffic management lies in its role in identifying speed limits that align with actual driver behavior. When traffic engineers conduct studies to determine appropriate speed limits, they collect data on the speeds at which vehicles are traveling on a particular road. The 85th percentile speed is the speed at or below which 85% of the vehicles are observed to travel.

This measurement is crucial because it reflects the speeds that the majority of drivers feel comfortable and safe traveling under normal conditions. Setting speed limits based on this data helps ensure that the limits are reasonable and accepted by the majority of drivers, which can lead to better compliance and, ultimately, safer roadways. By using driver behavior as a basis for speed limits, traffic management can create more effective and appropriate regulations that correspond with how drivers actually behave on the road.