Operating Speed on a Buffer-Separated Managed Lane

Abstract

Managed lanes typically are on or adjacent to freeways and are actively operated and managed to preserve operational performance—such as more optimal travel speeds—over comparable general-purpose traffic lanes. A study was conducted to evaluate speeds on existing buffer-separated managed lanes to identify variables that influence operating speed. Speed data from more than 130 unique sites in Los Angeles, California; Orange County, California; and Dallas, Texas, were used. All analyses showed that the managed lane volume and the speed in the general-purpose lanes were related to the speed in the managed lane (statistically significant). The Dallas analysis, which used speeds averaged by 1-min increments, showed that the factor with the most influence on uncongested managed lane speed was the managed lane’s geometry. The relationship between uncongested managed lane speed and the managed lane envelope (sum of left shoulder width, managed lane width, and buffer width) was found to be statistically significant. For each additional foot over a 16-ft envelope width, managed lane speed increased by approximately 3.2 mph. In contrast, the California analysis, which used speeds averaged by 1-h increments, showed that the variable having the most influence was the volume in the managed lane. The researchers theorized that the lack of a relationship between managed lane speed and geometry in California is related to those speeds being an average 1-h speed rather than the 1-min speeds available in Texas.