> The pace of a traffic stream is defined as the 10 mph increment in speed in which the highest percentage of drivers is observed. Doesn't the upper limit of t

> The pace of a traffic stream is defined as the 10 mph increment in speed in which the highest percentage of drivers is observed. Doesn't the upper limit of that usually match the 85th percentile speed of traffic? > There is very little benefit to increasing speed limits beyond the 85th percentile. Assuming traffic speeds follow a normal distribution, even those who exceed the 85th percentile speed don't exceed it by much (more than 5 mph). Beyond that, we're talking about 97th percentile speed or greater. > As vehicles speed up, the distance between vehicles increases and thus the total number of vehicles that can occupy a given segment of roadway is decreased. At 30 mph, about 36 vehicles can fit within a one mile stretch (assuming 3 second following distance, 15 ft long vehicles and one travel lane). Under the same assumptions only about 16 vehicles would fit in a one mile section at 70 mph. As traffic volume increases, the overall flow speed decreases which should offset the issues you noted.