Intermediate Access to Buffer-Separated Managed Lanes

A Texas Department of Transportation research project developed guidance on intermediate access to and from buffer-separated managed lanes located within general purpose lanes. For intermediate access openings, other communities recommend opening lengths between 1,300 ft and 2,000 ft (396 m to 610 m). While the recommended buffer width is 4 ft (1.2 m) or greater, many sites have a 2- to 3-ft (0.6- to 0.9-m) width. To assist in developing the guidance material, researchers recorded operations at five intermediate access sites. Characteristics measured included where the vehicle entered or left the managed lane (early, within one of two or three equal-distance zones, or late) and the lane of origin for the vehicle. A surprisingly large number of maneuvers (7%) was for vehicles passing a slower-moving vehicle. Approximately 9% of those moving into the high-occupancy vehicle (HOV) lane and 8% of those moving out of the HOV lane crossed the solid white markings (i.e., not in compliance with the pavement markings). The percentage of noncompliance increased to about 15% during those periods with low speeds [less than 40 mph (64 km/h)] or high speeds [greater than 60 mph (96 km/h)]. The percentage of maneuvers in compliance with the pavement markings varied by the length of the intermediate access opening. The compliance rate was greater for the longer access opening length [1,500 ft (457 m)] than for the shorter access opening length [1,160 ft (354 m)].