DEVELOPMENT AND OPERATIONAL ANALYSIS OF HIGHWAY ALTERNATING MERGE TRANSITION ZONES A Dissertation Submitted to Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Civil and Environmental Engineering By Wakeel Idewu B., University of Louisiana at Lafayette, 2004 M., Louisiana State University, 2007 August 2009 ACKNOWLEDGMENTS My tenure at Louisiana State University would not have been possible without the support of my family and friends. I would like to thank my wife, Roslyn Idewu, for her constant support and understanding throughout the years. I am truly a stronger and better person with her. My newborn son, Corban Idewu, has become a source of new motivation for me, so I would like to thank him for that and for helping me understand that there is always a reason to smile.
I would also like to thank the generations of the past, both within and outside of my family. My position is a result of their hard work, sacrifice and values. I especially thank my parents Wakeel O. Idewu and Tassin J.
Idewu for keeping me focused, involved, and exposed. Moreover, the encouragement I have received from my in-laws and friends have been energizing during tough periods. Financially, I would not have been able to survive if it were not for the support of the National Science Foundation, Office of Naval Research, and Minority Engineering Program. I thank Cheryle Peters for helping me get situated my first semester and stay grounded.
Most importantly she provided me the opportunity to grow as a teacher and leader by placing me in positions outside of my comfort zone. The friendly faces within the College of Engineering were always a joy to work with and talk to. I most enjoyed working with my major professor Dr. His contribution to my dissertation and growth as a researcher and future professor is invaluable.
I especially thank him and my advisory committee for their time, patience, constant support and technical advice. ii Lastly I would like to thank God for all of the above, and for directing my path. Throughout my life he has placed me in situations that either helped me grow stronger or wiser. I acknowledge that the individuals I have mentioned above were all part of his plan for my life and I am thankful to be given the opportunity to continue to grow mentally, physically, and spiritually.
iii TABLE OF CONTENTS ACKNOWLEDGMENTS. ii LIST OF TABLES. vi LIST OF FIGURES .3 Significance of Research .1 Work Zone Traffic Control Issue .2 Work Zone Capacity .3 The Components of a Merging Maneuver .1 Conventional Merge Strategy.2 Static Early Merge Strategy .3 Dynamic Early Merge strategies .5 Dynamic Late Merge .6 Always Close Right Lane.9 Zipping Concept Applied in the United States.1 Experimental Merge Design Selection .1 Joint Merge Concept .2 Selection of a Joint Merge Traffic Control Layout .2 Joint Merge Design Components .2 Traffic Control Devices .3 Traffic Control Layout .4 Description of the Study Site .1 Data Collection Devices .2 Data Collection Period .3 Data Aggregation and Reduction .6 Measures of Effectiveness .2 Queue Discharge Rate .4 Discharge Flow Rate Analysis .1 Joint Merge Development .1 Evaluation of the Joint Merge .2 Findings from the Evaluation .3 Vehicle Lane Distribution .3 Practical Application of the Joint Merge.4 Concerns with the Joint Merge. 83 APPENDIX A: SIGNS USED IN THE CDOT SURVEY QUESTIONNAIRE.
87 APPENDIX B: DATA RECORDED FROM THE TEST SITE. 88 APPENDIX C: JOINT MERGE TRAFFIC CONTROL SCHEMES. 101 APPENDIX D: DRIVER’S RESPONSE ON JOINT MERGE CONFIGURATION. 107 v LIST OF TABLES Table 1: Advance Warning Sign Measurements.
6 Table 2: HCM Measured Average Capacity for Lane Closures. 13 Table 3: Work Zone Traffic Control Merging Strategies. 28 Table 5: Placement of MIR Sensors for Both Merge Configurations. 49 Table 6: Programmed Speed Groups.
51 Table 7: Volume Classification. 52 Table 8: Observed Flow Values for Conventional and Joint Merge Configurations. 57 Table 9: General Speed Statistics at Zones E and D. 58 Table 10: Percentage of Vehicles Traveling in the Closed Lane.
64 Table 11: Tests of Between-Subjects Effects for Vehicles in Closed Lane. 65 Table 12: Percentage of Vehicles in the Closed Lane at Various Volume Levels. 66 Table 13: Tests of Between-Subjects Effects for Speed in the Closed Lane. 67 Table 14: Percent Change-in-Speed between Zones in the Closed Lane.
68 Table 15: Tests of Between-Subjects Effects for Percent Change in Speed in the. 69 Table 16: Percent Change in Speed between Zones in the Open Lane. 70 Table 17: Discharge Flow Rates. 71 Table 18: Joint and Conventional Merge Comparison Test for Discharge Flow Rates.
72 Table 19: Summary of Major Findings. 72 vi LIST OF FIGURES Figure 1: Lanes Involved in Merging Maneuvers. 3 Figure 2: Illustrated Warning Signs. 3 Figure 3: MUTCD Typical Applications of a “Stationary Lane Closure ”.
5 Figure 4: Symbolic Warning Signs. 14 Figure 5: Textual Warning Signs. 14 Figure 6: Dynamic Early Merge. 17 Figure 7: Late Merge Layout.
18 Figure 8: Zipper Strategy Sign Used in the Netherlands. 22 Figure 9: Experimental Merge Sign. 24 Figure 10: Mobile Bay Ferry Loading Area, Dauphin Island AL. 25 Figure 11: Pennsylvania Avenue Interchange of the Anacostia Freeway, D.
26 Figure 12: On Ramp Alternating Merge Traffic Pattern. 26 Figure 13: Joint Merge Configuration. 35 Figure 14: Conventional Merge Configuration. 36 Figure 15: Joint Merge Traffic Control Plan with Transition Zone Segment Coding.
37 Figure 16: Segments 2 and 3 of the Joint Merge Transition Zone. 38 Figure 17: Second Changeable Message Board. 39 Figure 18: Established Zones Used for Traffic Control Plan Analysis. 44 Figure 20: Flaggers near the Installation of MIRs.
47 Figure 21: Example of the Installation Process. 48 Figure 22: Attached MIR with Protective Cover. 48 Figure 23: Placement of MIRs. 49 vii Figure 24: Speed/Time and Volume/Time Graph Used in Selecting Flow Rates.
54 Figure 25: Fitted Curves Using Least Squares Estimate. 60 Figure 26: Comparison of Lane Distribution of Vehicles. 61 viii ABSTRACT The design and control of work zone traffic control areas is governed by standards published by the United States Department of Transportation (US-DOT) and documented in the Manual for Uniform Control Devices (MUTCD). While these configurations have evolved over time to reflect safer and more efficient management practices and have become familiar to drivers, they are also recognized as areas of vehicle conflict that can cause congestion and safety problems.
As part of this research, a new design has been developed that has the potential to lessen the detrimental effects of lane closures in work zones. This new concept, known as the “joint merge,” is configured to simultaneously merge two lanes into one. The key feature of the joint merge design is its use of a two-sided taper. In it, both lanes approaching a lane reduction are simultaneously tapered into a single lane, with neither lane having a priority, thereby influencing drivers to merge in a smooth alternating pattern.
The joint merge configuration was examined at a work zone site in Louisiana and compared to the MUTCD conventional merge configuration that was tested at the same site. The performance measures collected in the field included lane-specific volume and vehicle speeds. The two designs were quantitatively compared using Analysis of Variance (ANOVA) and T-test statistical procedures. These two testing agents were used to analyze the effects each design had on volume, speed and vehicle lane distributions at several locations in advance of the work zone entrance.
Using speed and volume data, the joint merge traffic control plan was found to increase the efficiency of the closed lane and better encourage the use of both lanes ix leading up to the work zone entrance. It was further concluded that the number of lane changes during low and high volume periods decreased when the joint merge configuration was used. While no conclusive findings could be made relative to its specific effect on capacity, the video recordings and lane usage data suggested that the joint merge strategy was understood and well received by most drivers. INTRODUCTION With more than 3,000 highway construction work zones in operation on the national highway system on any given day, there is an increasing need to provide safe and efficient mobility for vehicles traveling in the vicinity of the work zones (U.
Department of Transportation 2002). It has been estimated that the typical motorist encounters an active work zone almost every 100 miles (G. Therefore, driving past or near a construction zone has become a common occurrence for most drivers. However, fatalities from motor vehicle crashes in work zones increased approximately 50 percent between 1997 and 2003 (U.
Department of Transportation 2003). More specifically, 1,028 fatalities occurred in work zone related crashes, with an additional 40,000 injuries, in 2003 (National Cooperative Highway Research Program 2005). The increase in driver risk created by work zones are often attributed to roadway maintenance work, which often requires the closing of at least one lane during construction periods. Construction periods range from hours to years depending on the type of work being done and the specific conditions that exist at the site (i.
roadway type, roadway volume, posted speed limit, roadway configuration). There are three types of construction periods: short, intermediate, and long term. Short-term construction is typically accomplished during the day and lasts from one to twelve hours. Intermediate construction may be performed overnight but lasts no more than three days.
Any work anticipated to require more than three days of construction is classified as long-term work. Regardless of the work classification, construction in work zones requires the closure of at least one lane and often results in decreased capacity, an increase of hazards, and longer delays for drivers. 1 An important feature of the work zone configuration is the transition zone. In transition zones, available lanes gradually decrease and arriving traffic moves out of the lane baring construction.
Since lane closures reduce capacity, areas before the transition zone can become highly congested during heavy traffic periods with queues stretching for miles ahead of the transition zone. Another problem associated with transitions in work zones is driver dissatisfaction and frustration. A recent study found that a third of drivers were dissatisfied with work zones on highways (U. Department of Transportation 2001).
In addition to safety concerns, motorist dissatisfaction may be influenced by reduced capacity and increased travel time. Kim, Wang and Ulfarsson (2007), reported approximately 60 percent of freeway congestion is caused by “expected incidents” such as work zones or “unexpected events” such as crashes. Work zone lane closures have been shown to increase congestion during heavy volume periods. In low to medium volume conditions, transition zones function with few problems since there are numerous gaps of adequate size for drivers to change lanes.
Drivers in open lanes often adjust speed to create gap opportunities for merging drivers, similar to freeway on-ramp situations. However, once traffic demand reaches or exceeds capacity in transition areas, speeds rapidly drop and queues of slower-moving traffic begin to form. During high volume periods, these queues can extend upstream for long distances, intensifying driver frustration as conflicts arise between vehicles approaching the transition zone. Three lanes are involved in guiding vehicles through transition zones.
Throughout this study, those lanes are referred to as “closed”, “open”, and “merged” lanes and are shown in Figure 1. Open lanes are unaltered lanes for which vehicles traveling in them are not shifted laterally. Closed lanes terminate, and vehicles in them are required to transition to the adjacent 2 right or left lane depending on the configuration. Merged lanes are lanes downstream of the transition zone that carries traffic from both of the entry lanes.