Intermediate Access to Buffer-Separated Managed Lanes

K. Fitzpatrick, M.A. Brewer, E. Park
College Station, TX: Texas Transportation Institute
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Publication Abstract: 
The objective of this Texas Department of Transportation (TxDOT) research project was to develop guidance materials on intermediate access to a buffer-separated toll lane. To develop the material researchers gathered other state guidelines, reviewed the literature, and recorded operations at five intermediate access sites. From videotapes of the sites, characteristics of approximately 8400 vehicles that moved into or out of the managed lane were recorded. Examples of the characteristics measured included where the vehicle entered or left the lane (early, within the opening, or late) and the lane of origin for the vehicle. Volume counts for 5-minute periods were associated with each maneuver. Approximately 9 percent of the vehicles crossed the solid white markings (i.e., were not in compliance with the pavement markings). Compliance was better for the longer access opening length (1500 ft) as compared to the 1160-ft access opening length. A surprisingly large number of maneuvers at the intermediate access openings (over 7 percent) involve vehicles passing slower-moving vehicles. At the two sites with the larger quantity of data between 40 and 80 percent of the passing vehicles involved a vehicle leaving the managed lane to pass a slower-moving managed-lane vehicle. Findings from one field site demonstrated that when presented with the opportunity to enter a managed lane that is located very close to an entrance ramp, drivers will attempt to cross multiple lanes to do so.